These exercises use Polit2SetB. Use your choice of analysis program (Excel, SPSS, Intellectus Statistics) to respond to the following:
(1) Calculate the mean, standard deviation, minimum, maximum, and standard error of the mean (SEM) for the Body Mass Index (BMI) variable.
a. What is the mean, SD, and SEM for this sample?
b. Using the
z
formula for calculating confidence intervals, compute the 95% CI (confidence interval) and 99% CI (confidence interval) around the mean for BMI.
c. Using the
t
formula and the
t
distribution table posted this week, compute the 95% CI (confidence interval) and 99% CI (confidence interval) around the mean for BMI.
d. How do the confidence intervals you calculated in (b) and (c) compare to each other?
(2) Separate your data file into two groups (above poverty vs below poverty) using the woman’s poverty status (poverty) variable. Calculate the mean and SEM for each group using the Body Mass Index (BMI) variable.
a. What is the mean and SEM for each group?
b. What do you notice about the SEMs? Why do you think that is?
c. Using the formula of your choosing (z
or
t) compute the 95% CI (confidence interval) around the mean for BMI for each group.
(3) Using the one-sample
t-test, compare score on the Short-Form Health Survey (SF12) physical (sf12phys) and mental (sf12ment) scores to the national norms (M
= 50;
SD
= 10).
a. What would the null & alternative hypotheses be for these two analyses?
b. What are the
t
values for each of these analyses?
c. Were either of these values statistically significant? If so, at what level?
d. Write 1-2 sentences describing each of these results.
e. What are the 95% CI values for each analysis? What does each one mean?