In: Statistics and Probability
In a psychology experiment reported in American Statistician ,
25 female students completed a questionnaire measuring their fear
of negative evaluation ("FNE" – a higher score indicates greater
fear of negative evaluation). Eleven of the students were known to
suffer from the eating disorder bulimia. The FNE scores are given
here (scores of the bulimia sufferers in the top row).
10 13 13 14 16 19 20 21 21 24 25
6 7 8 10 11 13 13 15 16 18 19 19 20 23
1. What parameter did the psychologists investigate? In which
populations? What seems to be the point of this
investigation?
2. Compute the mean FNE score in each sample. Which group appears
to have the higher average FNE scores?
3. Use your calculator or other computational resource to verify
these 95% confidence intervals for mean FNE scores:
- students suffering from bulimia (14.5, 21.1)
- students with normal eating habits (11.1, 17.2)
- Describe the procedures you used.
4. What assumptions are required for these intervals to be
valid?
a) about the sample?
b) about the population?
5. Interpret each confidence interval with a sentence that begins
"I'm 95% sure that..."
5. Would 90% confidence intervals be wider or narrower?
Explain.
6. Notice that the two intervals overlap (the low end of the first
interval is lower than the high end of the second interval). What
does that say about the mean FNE scores of students in the two
populations?