Question

For each of the following claims, determine the null and alternative hypotheses. Then determine if the test is left-tailed, right-tailed, or two-tailed test. (b) According to a study published in March, 2006 the mean length of a phone call on a cellular telephone was 3.25 minutes. A researcher believes that the mean length of a call has increased since then.

Answer 1

(first part)

null hypothesis H0:3.25

alternate hypothesis Ha:>3.25

since  researcher believes that the mean length of a call has increased since then , it means is increased from 3.25. so alternate hypothesis would be >3.25 and opposite of it 3.25 would be the null hypothesis.

here is population mean length of a phone call

(second part) This is right tailed test .

The alternate hypothesis(H₁) determines if you have a right or left or two tailed test. In right tailed test alternate hypothesis statement contains a greater than (>) symbol.