Part I. Chi-Square Goodness of Fit Test (equal frequencies)
In order to determine staffing levels, a hospital wants to determine if births occur with the same frequency on each day of the week. The table below lists the days of the week selected by a random sample of 100 births. Consider the claim that the days of the week have the same frequency of a birth occurring.  
  
Sunday
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
 
32
16
7
20
11
8
6
Instructions for performing this test in Stat Disk can be found in the Stat Disk User’s Manual under Goodness of Fit, Equal Frequencies.
  
Instructions
Answers
 
1. Use   the Chi-Square Goodness-of-Fit test to see if there is a difference between   the frequency of births and days of the week.  Use a significance level of .01. 
Paste results here.
 
2. What   are we trying to show here?
 
3. What   is the p-value and what does it represent in the context of this problem?
 
4.  State in your own words what the results of   this Goodness-of-fit test tells us.
 
5. Repeat   the above procedure using only the weekdays Paste results here. Did you get different results? What do they mean?
Part II. Chi-Square Goodness of Fit Test (unequal frequencies)
In the 2000 U.S. Census, the ages of individuals in a small town were found to be the following:
Less than 18 – 20% 18-35 – 30%  and  greater than 35 – 50% 
In 2010 the ages of 500 individuals from the same small town were sampled with the following results:
Less than 18 – 121 people 18-35 – 288 people and greater than 35 – 91 people
Using an alpha of 0.05, would you conclude that the population distribution of ages has changed in the last 10 years? Instructions for performing this test in Stat Disk can be found in the Stat Disk User’s Manual under Goodness of Fit, Unequal Frequencies.
  
Instructions
Answers
 
6. Complete   the table as necessary. 
[Hint: You will   need to compute the observed frequencies based on the percentages for the 500   samples. Round to the nearest   integer.]
Less than 18
18-35
35-91
 
OBSERVED
121
288
91
 
EXPECTED
 
7. Use   the Chi-Square Goodness-of-Fit test for Unequal frequencies to see if there   is a difference between the observed frequencies and the expected frequencies   Use a significance level of .05. 
Paste results here.
 
8. State   the null and alternative hypothesis.
 
9. What   conclusion would you reach, given the result of your Goodness-of-Fit   test? [State in your own words   following the guidelines for a conclusion statement learned last week.]
Part III. Chi-Square Test of Independence
The following table is the result of a survey from a random sample of different crime victims. 
Use the data to test the claim that the type of crime is independent of whether the criminal was a stranger. Use a significance level of 0.05.
  
Homicide
Robbery
Assault
 
Criminal was a   stranger
12
379
727
 
Criminal was an   acquaintance or relative 
39
106
642
Hint: Instructions for performing this test in Stat Disk can be found in the Stat Disk User’s Manual under the heading Chi Square Test of Independence (Contingency Tables).
  
Instructions
Answers
 
10. Just   looking at the numbers in the table, what is your best guess about the   relationship between type of crime and criminal being a stranger or not? Are   they independent or is there a relationship? 
 
11. Compute a   Chi-Square Test of Independence on this data using a 0.05 level of significance. Paste your results here.
 
12. What are   the null and alternative hypothesis for this test?
 
13. What is   the p-value for this result? What does   this represent?
 
14. State   your conclusion related to the context of this problem.
Part IV. Apply this to your own situation
Using one of the above statistical tests, compose and SOLVE an actual problem from the context of your own personal or professional life. You will need to make up some data and describe which test you will use to analyze the situation. Here’s an example:
  
Example: Do not use this   problem!!
 
State the problem that you are analyzing. 
Last year, I asked the kids in my neighborhood what   kind of cookies they preferred. 50%   said chocolate-chip, 20% said oatmeal-raisin, and 30% said sugar cookie. I want to see if this has changed.
 
Make up some data for the new situation. 
I asked 50 neighborhood kids what kind of cookie they   preferred now and here’s what they said:
· 35 said chocolate-chip
· 5 said oatmeal-raisin
· 10 said sugar-cookie
 
Determine which type of Chi-Square test you will   perform.
Since these are unequal frequencies, I will perform a   Chi-Square Goodness-of-Fit Test (Unequal Frequencies).
 
Specify your null and alternative hypotheses.
H0: There is no   difference this year in the preferences of cookies within the neighborhood   kids.
H1: Things have   changed.
 
Setup the test
Chocolate-Chip
Oatmeal-Raisin
Sugar-Cookie
 
OBSERVED
35
5
10
 
EXPECTED
25
10
15
 
Perform the test
Paste   your STATDISK results here
 
State your conclusion
We have   evidence to believe ….
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Part I. Chi-Square Goodness of Fit Test (equal frequencies)
In order to determine staffing levels, a hospital wants to determine if births occur with the same frequency on each day of the week. The table below lists the days of the week selected by a random sample of 100 births. Consider the claim that the days of the week have the same frequency of a birth occurring.  
  
Sunday
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
 
32
16
7
20
11
8
6
Instructions for performing this test in Stat Disk can be found in the Stat Disk User’s Manual under Goodness of Fit, Equal Frequencies.
  
Instructions
Answers
 
1. Use   the Chi-Square Goodness-of-Fit test to see if there is a difference between   the frequency of births and days of the week.  Use a significance level of .01. 
Paste results here.
 
2. What   are we trying to show here?
 
3. What   is the p-value and what does it represent in the context of this problem?
 
4.  State in your own words what the results of   this Goodness-of-fit test tells us.
 
5. Repeat   the above procedure using only the weekdays Paste results here. Did you get different results? What do they mean?
Part II. Chi-Square Goodness of Fit Test (unequal frequencies)
In the 2000 U.S. Census, the ages of individuals in a small town were found to be the following:
Less than 18 – 20% 18-35 – 30%  and  greater than 35 – 50% 
In 2010 the ages of 500 individuals from the same small town were sampled with the following results:
Less than 18 – 121 people 18-35 – 288 people and greater than 35 – 91 people
Using an alpha of 0.05, would you conclude that the population distribution of ages has changed in the last 10 years? Instructions for performing this test in Stat Disk can be found in the Stat Disk User’s Manual under Goodness of Fit, Unequal Frequencies.
  
Instructions
Answers
 
6. Complete   the table as necessary. 
[Hint: You will   need to compute the observed frequencies based on the percentages for the 500   samples. Round to the nearest   integer.]
Less than 18
18-35
35-91
 
OBSERVED
121
288
91
 
EXPECTED
 
7. Use   the Chi-Square Goodness-of-Fit test for Unequal frequencies to see if there   is a difference between the observed frequencies and the expected frequencies   Use a significance level of .05. 
Paste results here.
 
8. State   the null and alternative hypothesis.
 
9. What   conclusion would you reach, given the result of your Goodness-of-Fit   test? [State in your own words   following the guidelines for a conclusion statement learned last week.]
Part III. Chi-Square Test of Independence
The following table is the result of a survey from a random sample of different crime victims. 
Use the data to test the claim that the type of crime is independent of whether the criminal was a stranger. Use a significance level of 0.05.
  
Homicide
Robbery
Assault
 
Criminal was a   stranger
12
379
727
 
Criminal was an   acquaintance or relative 
39
106
642
Hint: Instructions for performing this test in Stat Disk can be found in the Stat Disk User’s Manual under the heading Chi Square Test of Independence (Contingency Tables).
  
Instructions
Answers
 
10. Just   looking at the numbers in the table, what is your best guess about the   relationship between type of crime and criminal being a stranger or not? Are   they independent or is there a relationship? 
 
11. Compute a   Chi-Square Test of Independence on this data using a 0.05 level of significance. Paste your results here.
 
12. What are   the null and alternative hypothesis for this test?
 
13. What is   the p-value for this result? What does   this represent?
 
14. State   your conclusion related to the context of this problem.
Part IV. Apply this to your own situation
Using one of the above statistical tests, compose and SOLVE an actual problem from the context of your own personal or professional life. You will need to make up some data and describe which test you will use to analyze the situation. Here’s an example:
  
Example: Do not use this   problem!!
 
State the problem that you are analyzing. 
Last year, I asked the kids in my neighborhood what   kind of cookies they preferred. 50%   said chocolate-chip, 20% said oatmeal-raisin, and 30% said sugar cookie. I want to see if this has changed.
 
Make up some data for the new situation. 
I asked 50 neighborhood kids what kind of cookie they   preferred now and here’s what they said:
· 35 said chocolate-chip
· 5 said oatmeal-raisin
· 10 said sugar-cookie
 
Determine which type of Chi-Square test you will   perform.
Since these are unequal frequencies, I will perform a   Chi-Square Goodness-of-Fit Test (Unequal Frequencies).
 
Specify your null and alternative hypotheses.
H0: There is no   difference this year in the preferences of cookies within the neighborhood   kids.
H1: Things have   changed.
 
Setup the test
Chocolate-Chip
Oatmeal-Raisin
Sugar-Cookie
 
OBSERVED
35
5
10
 
EXPECTED
25
10
15
 
Perform the test
Paste   your STATDISK results here
 
State your conclusion
We have   evidence to believe ….

 

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