1.When do we use a t-statistic instead of a z-statistic to help infer a mean?

2.Identify whether the studies described here are based on (1) single samples, (2) paired samples, or (3) independent samples.

a.Cardiovascular disease risk factors are compared in husbands and wives.

b.A nutritional exam is applied to a random sample of individuals. Results are compared to the results of the whole nation.

c.An investigator compares vaccination histories in 30 autistic schoolchildren to a simple random sample of non-autistic children from the same school district.

3.Identify two graphical methods that can be used to compare quantitative (continuous) data between two independent groups.

4.A questionnaire measures an index of risk-taking behavior in respondents. Scores are standardized so that 100 represents the population average. The questionnaire is applied to a sample of teenage boys and girls. The data for boys is {72, 73, 86, 95, 95, 95, 96, 97, 99, 125}. The data for girls is {89, 92, 93, 98, 105, 106, 110, 126, 127, 130}. Explore the group differences with side-by-side boxplots.Create the boxplots and then describe how risk taking behavior varies between genders.

5.Which study will require a larger sample size, one done with 80% power or 90% power when alpha (type I error) is set at 0.05 and we use the same population and expected difference and variation for both studies?

6.True or False:When using data from the same sample, the 95% confidence interval for will always support the results from a 2-sided, 1 sample t-test.Explain your reasoning.