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제가 공부하는 분야에서는 (체육교육), T-test와 ANOVA를 많이 사용합니다. 처음에는 T-test 와 ANOVA 를 구분하기 어려워서 차이를 정리했었는데 정리한 것을 바탕으로 포스팅해 놓으렵니다.

쉽게 말하면 T-test와 ANOVA는 사실은 같은 방법을 사용합니다. 

분석하고자 하는 집단의 수가 T-test와 ANOVA를 결정합니다. 

T-test는 2 집단의 평균의 차이를 비교하고, ANOVA는 2 집단 이상의 평균의 차이를 비교하는데 사용합니다. 




예를 들어보자면,

1. 남자와 여자의 Physical activity level 을 비교한다고 하면, 집단(남자, 여자)로 2개이고 평균(Activity level 평균)을 비교하므로 이 경우에는 T-test를 사용해도 됩니다.  

2. 초등학교, 중학교, 고등학교 학생들의 Physical activity level 을 비교한다면, 3집단(초, 중, 고)의 평균을 비교하므로 이 경우에는 ANOVA(분산분석)를 사용합니다. 

두 가지 분석 방법(ANOVA는 T-test)들이 가지고 있는 분석 방법은 거의 비슷합니다.

또한, T-test를 하게 되면 검정 통계량 (test statistic) 은 T, ANOVA를 하게 되면 검정통계량은 F 를 이용하여 분석을 합니다. SPSS 프로그램을 사용하면 결과에 t 또는 f 값으로 나타납니다. 

아래 두 개 사진은 SPSS를 이용했을 때 얻는 결과들의 예시입니다. 




제가 언급했던 전반적인 내용을 간단하게 정리하자면 아래와 같습니다. 

                T-test               ANVOA
---------------------------------------------------------------
      차이           2 집단 평균비교     3집단이상 평균비교
            검정통계량                T                     F                
    제시통계량         평균, 표준편차       평균, 표준편차    
                                      사후검정 결과 


실제 데이터를 이용하면 이해하는 데 더 도움이 될 것 같습니다. 도움이 되셨길!!!




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항상 엑셀 틀고정하는 방법은 자주 쓰는데 자주 잊어버리기도 하죠! 

바로 본론으로! 쉽고 빠르게 틀고정을 해봅시다. 일단 틀고정 메뉴를 찾아야죠! 


1. 보기 메뉴에 보시면 틀고정 메뉴가 아래 사진처럼 보이시죠?


2. 틀고정을 클릭해 보시면 세 가지 메뉴가 나옵니다. 보통 첫행 고정을 많이 쓰지만 오늘은 특정 셀부분을 고정해보겠습니다.




3. 일단 한글 메뉴를 알았으니 연습은 영어메뉴에서 해볼까요? '틀고정' 선택 후 과정은 똑같아요! 일단 데이터를 간단하게 아래와 같이 만들었어요! 



4. 영어 메뉴에서는 Window - Freeze Panes 메뉴가 틀고정 메뉴입니다.





5. 아래 그림처럼 레이아웃 창에서 Window-Freeze Panes 메뉴를 찾을 수도 있어요!



6. 이제 메뉴를 찾았으니 셀 위에서 어디를 클릭하느냐가 가장 중요! 

아래 그림을 유심히 보시면 틀 고정 선택 후 가로 세로로 약간 굵은 선이 보이시죠? 틀 고정이 지정이 된 겁니다. 제가 어디를 클릭했는지도 보이시죠? E7 셀을 클릭을 했는데요. 왼쪽 번호열과 타이틀이 있는 행을 고정을 하려면 저 부분을 클릭해야 합니다. 항상 행과 열이 겹치는 부분이라 생각해서 '번호'가 적혀진 셀을 클릭했다가 틀리는 경우가 많으니 유의하세요!




7. 아래 사진은 틀고정 후 아래로 스크롤해본 건데요. 왼쪽 행을 보시면 행 번호가 6에서 27로 바뀌었죠? 바로 6번 행에서 틀 고정이 되서 '번호', '날짜', '데이터' 가 적힌 행을 항상 볼 수 있게 된 겁니다. 오른쪽으로 데이터를 이동하면 D 열이 고정이 되서 번호 열은 항상 보입니다.



8. 혹시 틀 고정을 잘 못해서 다시 고치려면 다시 같은 메뉴로 가서 틀고정을 해제하시면 됩니다. 


이상 간단 엑셀팁 틀고정하기였습니다!





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SUM

더하고자 하는 셀 범위에 있는 숫자를 모두 더할 때 유용합니다.

◈ 구문

SUM(number1,number2, ...)

간편하게 사용하기 위하여 자동합계 도구를 만들어 제공합니다. 자동합계 버튼을 도구모음에서 누르고 혹은 셀 위에서 '=sum'을 입력하시고 더하고자 하는 셀 범위를 드래그 하시면 쉽게 합을 구할 수 있습니다. 

단 문자열과 공백셀은 '0'으로 처리합니다.

◈ 주의

● 인수 목록으로 직접 입력한 숫자, 논리값, 숫자의 텍스트 표시는 계산됩니다.

 아래 나오는 예제 중 처음 두 예제를 참고하십시오.

● 숫자로 변환될 수 없는 텍스트나 오류 값을 인수로 사용하면 오류가 발생합니다.

● 1개부터 30개까지 사용할 수 있습니다.

◈ 예제      
       
데이터      
-5      
15      
30      
'5      
TRUE      
       
예제 수식 설명(결과) 결과
1 =SUM(3, 2) 3과 2를 더합니다. (5) 5
2 =SUM("5", 15, TRUE) 텍스트 값은 숫자로 변환되고, 논리값 TRUE는 숫자 1로 변환되므로, 5와 15와 1을 더합니다. (21) 21
3 =SUM(A22:A24) 위 열에서 처음 세 개의 숫자를 더합니다. (40) 40
4 =SUM(A22:A24, 15) 위 열에서 처음 세 개의 숫자와 15를 더합니다. (55) 55
5 =SUM(A25,A26, 2) 위의 마지막 두 개의 행에 있는 값을 더합니다. 참조 영역의 숫자가 아닌 값은 변환되지 않으므로 위 열의 값들은 무시됩니다. (2) 2

◈ 참고

COUNT : 인수 목록에서 숫자가 포함된 셀과 숫자의 개수를 계산합니다.

COUNTA : 인수 목록에서 공백이 아닌 셀과 값의 개수를 계산합니다.

AVERAGE : 인수의 산술 평균을 반환합니다.

PRODUCT : 인수를 모두 곱한 결과를 표시합니다.


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특별한 데이터를 SPSS로 구할 필요없이 단순히 P-value만 필요할 경우 P-value 구해주는 사이트입니다. 

아래 사진에서 보는 것과 같이 자유도(df)와 T-value 값만 있으면 P-value 값을 구할 수 있습니다. 

사이트 바로가기! <- 여기 클릭!





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가설 검정을 행할 때 범하는 두 가지 오류가 있습니다. 제1종 오류와 제2종 오류.  

두 오류의 위험은 역 관계에 있으며 검정의 유의 수준 및 검정력에 의해 결정됩니다. 즉, 위험을 정의하기 전에 어느 오류가 상황에 더 심각한 결과를 초래하는지 확인해야 합니다.

제1종 오류

귀무 가설이 참인데 기각하면 제1종 오류입니다. 
제1종 오류를 범할 확률은 α로, 가설 검정에 대해 설정한 유의 수준입니다. α가 0.05이면 귀무 가설을 잘못 기각할 가능성이 5%임을 인정하는 것입니다. 이 위험을 낮추기 위해서는 더 낮은 α 값을 사용해야 합니다. 그러나 더 낮은 알파 값을 사용하면 실제로 존재하는 실제 차이를 탐지할 가능성이 더 적습니다.
제2종 오류

귀무 가설이 거짓인데 기각하지 않으면 제2종 오류입니다. 
제2종 오류를 범할 확률은 β로, 검정의 검정력에 따라 달라집니다. 검정력을 충분하게 설정함으로써 제2종 오류를 범할 위험을 줄일 수 있습니다. 실제 존재하는 차이를 탐지할 수 있을 정도로 표본 크기를 크게 만들면 가능합니다.

거짓인 귀무 가설을 기각할 확률은 1–β와 같습니다. 이 값은 검정의 검정력입니다.



제1종 및 제2종 오류의 예

두 약품의 효과를 비교하는 연구에서 귀무 가설과 대립 가설은 다음과 같습니다.

  • 귀무 가설(H0): μ1= μ2

    두 약품의 효과가 동일합니다.

  • 대립 가설(H1): μ1≠ μ2

    두 약품의 효과가 동일하지 않습니다.

1종 오류: 두 약품이 다르지 않지만 연구자가 귀무 가설을 기각하고 두 약품이 다르다는 결론을 내리는 경우 

약품의 효과가 동일한 경우, 환자는 어느 약품을 복용하거나 관계 없이 동일한 수준의 효과를 얻기 때문에 연구자는 이 오류가 매우 심각한 것으로 생각하지 않을 수도 있습니다. 

2종 오류: 제2종 오류가 발생하면 귀무 가설을 기각해야 하지만 기각하지 못합니다. 즉, 연구자 두 약품이 실제로는 다르지만 같다는 결론이 2종 오류이기 때문입니다. 이 오류는 효과가 더 낮은 약품이 효과가 더 높은 약품 대신 판매될 경우 큰 위험을 가져올 수 있겠죠?




다른 예를 들어보면,

가설 검정을 할 때는 항상 제1종 오류 (Type 1 Error) 및 제2종 오류 (Type 2 Error)의 위험을 고려해야 합니다. 




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[엑셀 함수 정리] ROUND 함수

: 숫자를 지정한 자릿수로 반올림합니다.

◈ 구문

ROUND(number,num_digits)

◈ 주의

● Num_digits가 0보다 크면 숫자는 지정한 소수 자릿수로 반올림됩니다.

● Num_digits가 0이면 가장 가까운 정수로 반올림됩니다.

● Num_digits가 0보다 작으면 소수점 왼쪽에서 반올림됩니다.

◈ 예제      
       

예제

수식

설명(결과)

결과

1

=ROUND(2.15, 1)

2.15를 소수점 한 자리로 반올림합니다. (2.2)

2.2

2

=ROUND(2.149, 1)

2.149를 소수점 한 자리로 반올림합니다. (2.1)

2.1

3

=ROUND(-1.475, 2)

-1.475를 소수점 두 자리로 반올림합니다. (-1.48)

-1.48

4

=ROUND(21.5, -1)

21.5를 소수점 왼쪽 한 자리로 반올림합니다. (20)

20

◈ 참고

ROUNDUP : 0에서 먼 방향으로 수를 올림합니다.

ROUNDDOWN : 0에 가까운 방향으로 내림합니다.

INT : 가장 가까운 정수로 내립니다.

TRUNC : 숫자의 소수점 이하를 버리고 정수로 변환합니다.




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APA 논문 작성시 구두점 (Punctuation) 사용법


Comma

Use a comma to join 2 independent clauses by a comma and a coordinating conjunction (and, but, or, for, nor, so).

두 독립절을 이을 때 콤마 사용

Road construction can be inconvenient, but it is necessary.
The new house has a large fenced backyard, so I am sure our dog will enjoy it.

Use a comma after an introductory phrase, prepositional phrase, or dependent clause.

To get a good grade, you must complete all your assignments.
Because Dad caught the chicken pox, we canceled our vacation.
After the wedding, the guests attended the reception.

Use a comma to separate elements in a series. Although there is no set rule that requires a comma before the last item in a series, it seems to be a general academic convention to include it. The examples below demonstrate this trend.

On her vacation, Lisa visited Greece, Spain, and Italy.
In their speeches, many of the candidates promised to help protect the environment, bring about world peace, and end world hunger.

Use a comma to separate nonessential elements from a sentence. More specifically, when a sentence includes information that is not crucial to the message or intent of the sentence, enclose it in or separate it by commas.

John's truck, a red Chevrolet, needs new tires.
When he realized he had overslept, Matt rushed to his car and hurried to work.

Use a comma between coordinate adjectives (adjectives that are equal and reversible).

The irritable, fidgety crowd waited impatiently for the rally speeches to begin.
The sturdy, compact suitcase made a perfect gift.

Use a comma after a transitional element (however, therefore, nonetheless, also, otherwise, finally, instead, thus, of course, above all, for example, in other words, as a result, on the other hand, in conclusion, in addition)

For example, the Red Sox, Yankees, and Indians are popular baseball teams.
If you really want to get a good grade this semester, however, you must complete all assignments, attend class, and study your notes.

Use a comma with quoted words.

"Yes," she promised. Todd replied, saying, "I will be back this afternoon."

Avoid comma splices (two independent clauses joined only by a comma). Instead, separate the clauses with a period, with a comma followed by a coordinating conjunction, or with a semicolon.

Semicolon

Use a semicolon to join 2 independent clauses when the second clause restates the first or when the two clauses are of equal emphasis.

세미콜론 사용: 두 개 독립절을 연결할 때 두 번째 절이 첫 번째랑 연관이 있거나 두 개 절이 동등할 때. 

Road construction in Dallas has hindered travel around town; streets have become covered with bulldozers, trucks, and cones.

Use a semicolon to join 2 independent clauses when the second clause begins with a conjunctive adverb (however, therefore, moreover, furthermore, thus, meanwhile, nonetheless, otherwise) or a transition (in fact, for example, that is, for instance, in addition, in other words, on the other hand, even so).

두 독립절을 이을 때 첫 문장 다음에 연결부사가 있으면 세미콜론 사용

Terrorism in the United States has become a recent concern; in fact, the concern for America's safety has led to an awareness of global terrorism.

Use a semicolon to join elements of a series when individual items of the series already include commas.

Recent sites of the Olympic Games include Athens, Greece; Salt Lake City, Utah; Sydney, Australia; Nagano, Japan.

Colon

Use a colon to join 2 independent clauses when you wish to emphasize the second clause.

콜론 사용: 두 개 독립절을 연결하는데 두 번째 절을 강조하고 싶을 때

Road construction in Dallas has hindered travel around town: parts of Main, Fifth, and West Street are closed during the construction.

Use a colon after an independent clause when it is followed by a list, a quotation, appositive, or other idea directly related to the independent clause.

Julie went to the store for some groceries: milk, bread, coffee, and cheese.
In his Gettysburg Address, Abraham Lincoln urges Americans to rededicate themselves to the unfinished work of the deceased soldiers: "It is for us the living rather to be dedicated here to the unfinished work which they who fought here have thus far so nobly advanced. It is rather for us to be here dedicated to the great task remaining before us — that from these honored dead we take increased devotion to that cause for which they gave the last full measure of devotion — that we here highly resolve that these dead shall not have died in vain, that this nation under God shall have a new birth of freedom, and that government of the people, by the people, for the people shall not perish from the earth."
I know the perfect job for her: a politician.


Parenthesis

Parentheses are used to emphasize content. They place more emphasis on the enclosed content than commas. Use parentheses to set off nonessential material, such as dates, clarifying information, or sources, from a sentence.

Muhammed Ali (1942-present), arguably the greatest athlete of all time, claimed he would "float like a butterfly, sting like a bee."

Dash

Dashes are used to set off or emphasize the content enclosed within dashes or the content that follows a dash. Dashes place more emphasis on this content than parentheses.

Perhaps one reason why the term has been so problematic—so resistant to definition, and yet so transitory in those definitions—is because of its multitude of applications.
In terms of public legitimacy—that is, in terms of garnering support from state legislators, parents, donors, and university administrators—English departments are primarily places where advanced literacy is taught.
The U.S.S. Constitution became known as "Old Ironsides" during the War of 1812—during which the cannonballs fired from the British H.M.S. Guerriere merely bounced off the sides of the Constitution.
To some of you, my proposals may seem radical—even revolutionary.

Use a dash to set off an appositive phrase that already includes commas. An appositive is a word that adds explanatory or clarifying information to the noun that precedes it.

The cousins—Tina, Todd, and Sam—arrived at the party together.

Quotation Marks

Use quotation marks to enclose direct quotations. Note that commas and periods are placed inside the closing quotation mark, and colons and semicolons are placed outside. The placement of question and exclamation marks depends on the situation.

He asked, "When will you be arriving?" I answered, "Sometime after 6:30."

Use quotation marks to indicate the novel, ironic, or reserved use of a word.

History is stained with blood spilled in the name of "justice."

Use quotation marks around the titles of short poems, song titles, short stories, magazine or newspaper articles, essays, speeches, chapter titles, short films, and episodes of television or radio shows.

"Self-Reliance," by Ralph Waldo Emerson
"Just Like a Woman," by Bob Dylan
"The Smelly Car," an episode of Seinfeld

Do not use quotation marks in indirect or block quotations.

Italics

Underlining and Italics are often used interchangeably. Before word-processing programs were widely available, writers would underline certain words to indicate to publishers to italicize whatever was underlined. Although the general trend has been moving toward italicizing instead of underlining, you should remain consistent with your choice throughout your paper. To be safe, you could check with your teacher to find out which he/she prefers. Italicize the titles of magazines, books, newspapers, academic journals, films, television shows, long poems, plays of three or more acts, operas, musical albums, works of art, websites, and individual trains, planes, or ships.

Time
Romeo and Juliet by William Shakespeare
The Metamorphosis of Narcissus by Salvador Dali
Amazon.com
Titanic

Italicize foreign words.

Semper fi, the motto of the U.S. Marine Corps, means "always faithful."

Italicize a word or phrase to add emphasis.

The truth is of utmost concern!

Italicize a word when referring to that word.

The word justice is often misunderstood and therefore misused.


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https://owl.english.purdue.edu/owl/resource/560/06/

Reference List: Author/Authors

Single Author

Last name first, followed by author initials.

Berndt, T. J. (2002). Friendship quality and social development. Current Directions in Psychological Science, 11, 7-10.

Two Authors

List by their last names and initials. Use the ampersand instead of "and."

Wegener, D. T., & Petty, R. E. (1994). Mood management across affective states: The hedonic contingency hypothesis. Journal of Personality and Social Psychology, 66, 1034-1048.

Three to Seven Authors

List by last names and initials; commas separate author names, while the last author name is preceded again by ampersand.

Kernis, M. H., Cornell, D. P., Sun, C. R., Berry, A., Harlow, T., & Bach, J. S. (1993). There's more to self-esteem than whether it is high or low: The importance of stability of self-esteem. Journal of Personality and Social Psychology, 65, 1190-1204.

More Than Seven Authors

List by last names and initials; commas separate author names. After the sixth author's name, use an ellipses in place of the author names. Then provide the final author name. There should be no more than seven names. 

Miller, F. H., Choi, M. J., Angeli, L. L., Harland, A. A., Stamos, J. A., Thomas, S. T., . . . Rubin, L. H. (2009). Web site usability for the blind and low-vision user. Technical Communication, 57, 323-335.

Organization as Author

American Psychological Association. (2003).

Unknown Author

Merriam-Webster's collegiate dictionary (10th ed.).(1993). Springfield, MA: Merriam-Webster.

NOTE: When your essay includes parenthetical citations of sources with no author named, use a shortened version of the source's title instead of an author's name. Use quotation marks and italics as appropriate. For example, parenthetical citations of the source above would appear as follows: (Merriam-Webster's, 1993).

Two or More Works by the Same Author

Use the author's name for all entries and list the entries by the year (earliest comes first).

Berndt, T. J. (1981).

Berndt, T. J. (1999).

When an author appears both as a sole author and, in another citation, as the first author of a group, list the one-author entries first.

Berndt, T. J. (1999). Friends' influence on students' adjustment to school. Educational Psychologist, 34, 15-28.

Berndt, T. J., & Keefe, K. (1995). Friends' influence on adolescents' adjustment to school. Child Development, 66, 1312-1329.

References that have the same first author and different second and/or third authors are arranged alphabetically by the last name of the second author, or the last name of the third if the first and second authors are the same.

Wegener, D. T., Kerr, N. L., Fleming, M. A., & Petty, R. E. (2000). Flexible corrections of juror judgments: Implications for jury instructions. Psychology, Public Policy, and Law, 6, 629-654.

Wegener, D. T., Petty, R. E., & Klein, D. J. (1994). Effects of mood on high elaboration attitude change: The mediating role of likelihood judgments. European Journal of Social Psychology, 24, 25-43.

Two or More Works by the Same Author in the Same Year

If you are using more than one reference by the same author (or the same group of authors listed in the same order) published in the same year, organize them in the reference list alphabetically by the title of the article or chapter. Then assign letter suffixes to the year. Refer to these sources in your essay as they appear in your reference list, e.g.: "Berdnt (1981a) makes similar claims..."

Berndt, T. J. (1981a). Age changes and changes over time in prosocial intentions and behavior between friends. Developmental Psychology, 17, 408-416.

Berndt, T. J. (1981b). Effects of friendship on prosocial intentions and behavior. Child Development, 52, 636-643.

Introductions, Prefaces, Forewords, and Afterwords

Cite the publishing information about a book as usual, but cite Introduction, Preface, Foreword, or Afterword (whatever title is applicable) as the chapter of the book.

Funk, R., & Kolln, M. (1998). Introduction. In E. W. Ludlow (Ed.), Understanding English grammar (pp. 1-2). Needham, MA: Allyn and Bacon.


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https://owl.english.purdue.edu/owl/resource/560/03/

Citing an Author or Authors (In-Text Citations: Author/Authors)

A Work by Two Authors: Name both authors in the signal phrase or in the parentheses each time you cite the work. Use the word "and" between the authors' names within the text and use the ampersand in the parentheses.

Research by Wegener and Petty (1994) supports...
(Wegener & Petty, 1994)

A Work by Three to Five Authors: List all the authors in the signal phrase or in parentheses the first time you cite the source. Use the word "and" between the authors' names within the text and use the ampersand in the parentheses.

(Kernis, Cornell, Sun, Berry, & Harlow, 1993)

In subsequent citations, only use the first author's last name followed by "et al." in the signal phrase or in parentheses.

(Kernis et al., 1993)
In et al., et should not be followed by a period.

Six or More Authors: Use the first author's name followed by et al. in the signal phrase or in parentheses.

Harris et al. (2001) argued...
(Harris et al., 2001)

Unknown Author: If the work does not have an author, cite the source by its title in the signal phrase or use the first word or two in the parentheses. Titles of books and reports are italicized or underlined; titles of articles, chapters, and web pages are in quotation marks.

A similar study was done of students learning to format research papers ("Using APA," 2001).

Note: In the rare case the "Anonymous" is used for the author, treat it as the author's name (Anonymous, 2001). In the reference list, use the name Anonymous as the author.

Organization as an Author: If the author is an organization or a government agency, mention the organization in the signal phrase or in the parenthetical citation the first time you cite the source.

According to the American Psychological Association (2000),...

If the organization has a well-known abbreviation, include the abbreviation in brackets the first time the source is cited and then use only the abbreviation in later citations.

First citation: (Mothers Against Drunk Driving [MADD], 2000)
Second citation: (MADD, 2000)

Two or More Works in the Same Parentheses: When your parenthetical citation includes two or more works, order them the same way they appear in the reference list (viz., alphabetically), separated by a semi-colon.

(Berndt, 2002; Harlow, 1983)

Authors With the Same Last Name: To prevent confusion, use first initials with the last names.

(E. Johnson, 2001; L. Johnson, 1998)

Two or More Works by the Same Author in the Same Year: If you have two sources by the same author in the same year, use lower-case letters (a, b, c) with the year to order the entries in the reference list. Use the lower-case letters with the year in the in-text citation.

Research by Berndt (1981a) illustrated that...

Introductions, Prefaces, Forewords, and Afterwords: When citing an Introduction, Preface, Foreword, or Afterwords in-text, cite the appropriate author and year as usual.

(Funk & Kolln, 1992)

Personal Communication: For interviews, letters, e-mails, and other person-to-person communication, cite the communicator's name, the fact that it was personal communication, and the date of the communication. Do not include personal communication in the reference list.

(E. Robbins, personal communication, January 4, 2001).
A. P. Smith also claimed that many of her students had difficulties with APA style (personal communication, November 3, 2002).

Citing Indirect Sources

If you use a source that was cited in another source, name the original source in your signal phrase. List the secondary source in your reference list and include the secondary source in the parentheses.

Johnson argued that...(as cited in Smith, 2003, p. 102).

Note: When citing material in parentheses, set off the citation with a comma, as above. Also, try to locate the original material and cite the original source.

Electronic Sources

If possible, cite an electronic document the same as any other document by using the author-date style.

Kenneth (2000) explained...

Unknown Author and Unknown Date: If no author or date is given, use the title in your signal phrase or the first word or two of the title in the parentheses and use the abbreviation "n.d." (for "no date").

Another study of students and research decisions discovered that students succeeded with tutoring ("Tutoring and APA," n.d.).

Sources Without Page Numbers

When an electronic source lacks page numbers, you should try to include information that will help readers find the passage being cited. When an electronic document has numbered paragraphs, use the abbreviation "para." followed by the paragraph number (Hall, 2001, para. 5). If the paragraphs are not numbered and the document includes headings, provide the appropriate heading and specify the paragraph under that heading. Note that in some electronic sources, like Web pages, people can use the Find function in their browser to locate any passages you cite.

According to Smith (1997), ... (Mind over Matter section, para. 6).

Note: Never use the page numbers of Web pages you print out; different computers print Web pages with different pagination.




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Lab 4: Association and Regression

In this lab, we will investigate how total time spent on homework is associated with a student’s grades among the national sample of 10th grade students given in the NELS data collected in 1990. Follow the directions below to complete the analysis with SPSS.

Print out the outputs and submit in print. Also submit this worksheet with your answers to the questions.

  1. Open the SPSS dataset of “short NELS” that you created in Lab 1. If you don’t have the SPSS dataset ready to use, download the original data file “short_nels.csv” from Blackboard and follow Lab 1 Problem Set 2 to import it into SPSS.

  2. Download “nels_coding_system.pdf” from Blackboard. Follow the prompts below to locate the two variables of interest (i.e., time on homework, grades) in the dataset and learn about their coding systems.

    1. Open “nels_coding_system.pdf”. Search the keyword “homework” to learn about all variables related to homework available in this dataset.

    2. Find out the variable that is total time spent on homework out of school in 10th grade. Write down its variable name here.

      (Note: NELS is a longitudinal study that followed the sampled students over 12 years and collected data in 4 waves. The first wave was done in 1988 when students were in their 8th grade, which is also called the “base year”. The variables from this base year have their names starting with “by”. The 10th grade is the first follow-up wave and the variable names start with “f1”.)

    3. The dependent variable, student grades, is named ffugrad in the SPSS dataset. This is a composite score created by averaging each student’s math (f1s39a), English (f1s39b), history (f1s39c), and science (f1s39d) grades at the 10th grade.

    4. Use the variable names mentioned above as the keywords for searching the coding system PDF. This will lead you to coding systems of these variables, that is, what are the possible values this variable can assume, and what does each value represent. Write down the coding systems for the two variables of interest in the space below.

      (Note: ffugrad does not have its own coding system explained in the file. But because ffugrad is a composite score created using subject-specific grade variables, we can use one of the original variables, such as f1s39a, to find the coding system.

  3. Go to the SPSS. Follow the directions below to create a new, simpler dataset that includes only the variables of interest above.

    1. Open a new blank dataset: FileNewData

    2. Follow the directions below two times to copy and paste each of the two variables above

      from the short NELS dataset to the new dataset.

      Go to the short NELS SPSS data, Data ViewEditGo to VariableEnter the variable name in the text boxGoSelect the entire column, right-click and CopyGo to the new blank dataset, Data ViewSelect the first (blank) column, right-click and Paste.

    3. After both variables have been pasted into the new data file, save the new dataset.

    1. As the coding systems found above show, neither of these two variables of interest is a perfect continuous measure. For this lab’s purposes, we will treat ffugrad as if it’s a continuous measure. But for time on homework, follow the directions below to convert it into a more reasonably continuous measure --- hours.

      Open the new (simpler) SPSS dataset, Data ViewTransformRecode into Different VariablesSelect the homework variable (f1s36a2) as the Input VariableEnter homework as the Output Variable Name, click ChangeClick Old and New ValuesFor each pair of old (current) and new values below, enter the old and the corresponding new values in the text boxes then click AddAfter all pairs are defined, click ContinueOK


    1. Follow the directions below to create a scatter plot of the two variables. On the side of the printed graph, interpret the relation between the two variables.

      GraphsLegacy DialogsScatter/DotSimple ScatterSelect ffugrad for the Y Axis, select homework for the X Axis, create a title for the graphOK.

    2. Follow the directions below to find the Pearson’s correlation coefficient between the two variables. On the printed output, highlight/circle the Pearson’s correlation coefficient value, and then interpret this quantity on the side in terms of the direction and strength of the linear association between time on homework out of school and grades.

      AnalyzeCorrelateBivariateSelect ffugrad and homework as the VariablesOK.

    3. Follow the directions below to build a simple linear regression model to predict grades using

    the total time spent on homework out of school.

    1. Add a fitted linear regression line on the scatter plot.
      Go to the
      output window, double-click the scatter plotElementsFit Line at Total

      Apply.

    2. Run the linear regression model analysis.

      AnalyzeRegressionLinearDependent: ffugrad; Independent: homeworkOK.

    3. Write out the fitted model using the coefficients given in the outputs.

    4. Interpret the intercept.

    5. Interpret the slope.

    6. Find out the R2 value from the outputs and interpret it. 

Lab 4.sav


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