1. In a sample of 49 adolescents who served as the subjects in an immunologic study, one variable of interest was the diameter of a skin test reaction to an allergen. The sample mean and standard deviation were 21 and 11 mm erythema, respectively.

a. Use the Z or t-distribution? Why?

b. One-sided or two-sided test? Why?

c. Can it be concluded from these data that the population mean is less than 24 mm erythema?

d. What is the range on the p-value from the table that has percentiles of the t distribution? (link under References).

References:

1) Z-tables: http://www.z-table.com/

2) Percentiles of t distribution link:

http://personal.psu.edu/acq/401/tables/t.pdf

According to my book,

df = 0.10 = 90% (link)

df = 0.05 = 95% (link)

df = 0.025 = 97.5% (link)

df= 0.01 = 99% (link)

df = 0.005 = 99.5% (link)

df = 0.0005 = 99.9% (link)