Question

Probability and Statistics
Could you please solve the following questions with specifying the answers

A. When would you use a t-test rather than a z-test?

a. when you need to use the standard deviation of a small sample  

b. when the mean is very large  

c. when you want the confidence interval to be narrower

B. Twenty-five weighings of a small object on a sensitive scale result in average of 8.23 grams. If the standard deviation σ of weighings on this scale is .15 grams, what is a 95% confidence interval for the true weight of the object?

a. 8.23 ±.02         b. 8.23 ±.04        c.  8.23 ±.06       d.  8.23 ±.08

C. Randomly choose one of the 275 people in a certain organization. What is the conditional probability the person chosen is a non-smoker give the person is a woman?

Men who smoke - 40	Men who don’t spoke – 95
Women who smoke - 50	Women who don’t smoke - 90
90 total	185 total

1. 90/185      b. 90/140      c. 1-95/185       d.  90/275

Answer 1