What percent of the students have both waking-life and bedtime symptoms?.
As part of the study on ongoing fright symptoms due to exposure to horror movies at a young age, the following table was presented to describe the lasting impact these movies have had during bedtime and waking life:
Waking
symptoms
Bedtime symptoms Yes No
Yes 35 33
No 32 19
(a) What percent of the students have lasting waking-life symptoms? (Round your answer to two decimal places.)
%
(b) What percent of the students have both waking-life and bedtime symptoms? (Round your answer to two decimal places.)
%
(c) Test whether there is an association between waking-life and bedtime symptoms. State the null and alternative hypotheses. (Use α = 0.01.)
Null Hypothesis:
H0: There is no relationship between waking and bedtime symptoms.H0: Waking symptoms cause bedtime symptoms. H0: There is a relationship between waking and bedtime symptoms.H0: Bedtime symptoms cause waking symptoms.
Alternative Hypothesis:
Ha: Bedtime symptoms cause waking symptoms.Ha: Waking symptoms cause bedtime symptoms. Ha: There is a relationship between waking and bedtime symptoms.Ha: There is no relationship between waking and bedtime symptoms.
State the χ2 statistic and the P-value. (Round your answers for χ2 and the P-value to three decimal places.)
χ2 =
df =
P =
Conclusion:
We have enough evidence to conclude that there is a relationship.We do not have enough evidence to conclude that there is a relationship.
Here are the row and column totals for a two-way table with two rows and two columns.
a b 200
c d 200
200 200 400
Find two different sets of counts a, b, c, and d for the body of the table. This demonstrates that the relationship between two variables cannot be obtained solely from the two marginal distributions of the variables. (Start with the given value of a.)
a b c d
Set 1 30
Set 2 115
A study examined patterns and characteristics of volunteer service for young people from high school through early adulthood. Here are some data that can be used to compare males and females on participation in unpaid volunteer service or community service and motivation for participation.
Participants
Motivation
Gender Strictly Voluntary Court-ordered Other Non-participants
Men 31.1% 3.8% 7.2% 57.9%
Women 42.3% 1.5% 7.8% 48.4%
Note that the percents in each row sum to 100%.
(a) Graphically compare the volunteer-service profiles for men and women. Describe any differences that are striking.
Men dominate every category.There are no striking differences. Women dominate every category.Women have a noticeably higher percentage in the strictly voluntary category.
(b) Find the proportion of men who volunteer. Do the same for women. Compute the relative risk of being a volunteer for females versus males. (Round your answer for relative risk to two decimal places.)
Men
Women
Relative risk
Write a clear sentence contrasting females and males using relative risk as your numerical summary.
Men and women participate equally.A higher percentage of women were participants. A higher percentage of men were participants.none of the above
In what ways do advertisers in magazines use sexual imagery to appeal to youth? One study classified each of 1509 full-page or larger ads as “not sexual” or “sexual,” according to the amount and style of the dress of the male or female model in the ad. The ads were also classified according to the target readership of the magazine. Here is the two-way table of counts.
Magazine readership
Model dress Women Men General interest Total
Not sexual 360 522 242 1124
Sexual 201 94 90 385
Total 561 616 332 1509
(a) Summarize the data numerically and graphically. (Compute the conditional distribution of model dress for each audience. Round your answers to three decimal places.)
Women Men General
Not sexual
Sexual
(b) Perform the significance test that compares the model dress for the three categories of magazine readership. Summarize the results of your test and give your conclusion. (Use α = 0.01. Round your value for χ2 to two decimal places, and round your P-value to four decimal places.)
χ2 =
P-value =
Conclusion
Reject the null hypothesis. There is not significant evidence of an association between target audience and model dress.Fail to reject the null hypothesis. There is not significant evidence of an association between target audience and model dress. Reject the null hypothesis. There is significant evidence of an association between target audience and model dress.Fail to reject the null hypothesis. There is significant evidence of an association between target audience and model dress.
(c) All of the ads were taken from the March, July, and November issues of six magazines in one year. Discuss this fact from the viewpoint of the validity of the significance test and the interpretation of the results.
This is an SRS. This gives us no reason to believe our conclusions are suspect.This is not an SRS. This gives us no reason to believe our conclusions are suspect. This is an SRS. This gives us reason to believe our conclusions might be suspect.This is not an SRS. This gives us reason to believe our conclusions might be suspect.
A research project based on a study of older adults examined the relationship between physical activity and pet ownership. The data collected included information concerning pet owner characteristics and the type of pet owned. Here are data giving the relationship between pet ownership status and
What percent of the students have both waking-life and bedtime symptoms?
