The mean ±1 sd of ln [calcium intake (mg)] among 25 females, 12 to 14 years of age, below the poverty level is 6.56 ± 0.64.
The mean ±1 sd of ln [calcium intake (mg)] among 25
females, 12 to 14 years of age, below the poverty level is
6.56 ± 0.64. Similarly, the mean ± 1 sd of ln [calcium intake
(mg)] among 40 females, 12 to 14 years of age, above the
poverty level is 6.80 ± 0.76.
8.2) Test for a significant difference between the variances
of the two groups.
8.3)What is the appropriate procedure to test for a significant difference in means between the two groups?
8.4) Implement the procedure in Problem 8.3 using the
critical-value method.
8.5)What is the p-value corresponding to your answer to
Problem 8.4?
8.6 )Compute a 95% CI for the difference in means
between the two groups.
8.7 )Suppose an equal number of 12- to 14-year-old girls
below and above the poverty level are recruited to study
differences in calcium intake. How many girls should be
recruited to have an 80% chance of detecting a significant
difference using a two-sided test with α = .05?
8.8) Answer Problem 8.7 if a one-sided rather than a twosided test is used.
8.9) Using a two-sided test with α = .05, answer Problem
8.7, anticipating that two girls above the poverty level will
be recruited for every one girl below the poverty level who
is recruited.
8.10) Suppose 50 girls above the poverty level and 50
girls below the poverty level are recruited for the study.
How much power will the study have of finding a significant
difference using a two-sided test with α = .05, assuming
that the population parameters are the same as the sample
estimates in Problem 8.2?
8.11) Answer Problem 8.10 assuming a one-sided rather
than a two-sided test is used.
8.12) Suppose 50 girls above the poverty level and 25
girls below the poverty level are recruited for the study. How
much power will the study have if a two-sided test is used
with α = .05?
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