1. The belief is that the mean number of hours per week of part-time work of high school seniors in a city is 10.7 hours. Data from a simple random sample of 28 seniors indicated that their mean number of parttime work was 12.5 with a standard deviation of 1.3. Test whether these data cast doubt on the current belief. (use α = 0.05)
a.)State your null and alternative hypotheses.
b.)Sketch the rejection region.
c.) Calculate the test statistic. Plot this value in your sketch in part b.
d.) Determine the P-value for your test.
e.) State your conclusions clearly in complete sentences.
2.
A study of iron deficiency in infants compared samples of infants whose mothers chose different ways of feeding them. One group contained breast-fed infants. The children in another group were fed a standard baby formula without any iron supplements. Her are summary results on blood hemoglobin levels at 12 months of age:
Group | n |
mean x |
s |
Breast-fed | 25 | 15.4 | 2.2 |
Formula | 32 | 17.1 | 1.9 |
Part a: We want to see if the mean hemoglobin level is greater among formula-fed babies. State the hypotheses and perform the significance test on your hypothesis. Report the test statistic and p-value. State your conclusion in terms of the issue.
Part b: Give a 95% confidence interval for the mean difference in hemoglobin level between the two populations of infants.
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