Question

Suppose that a recent article stated that the mean time spent in jail by a first-time convicted burglar is 2.5 years. A study was then done to see if the mean time has increased in the new century. A random sample of 26 first-time convicted burglars in a recent year was picked. The mean length of time in jail from the survey was 3 years with a standard deviation of 1.8 years.Suppose that it is somehow known that the population standard deviation is 1.5. If you were conducting a hypothesis test to determine if the mean length of jail time has increased, what would the null and alternative hypotheses be? The distribution of the population is normal.(a) null hypothesis H0: μ = 2.5 yearsH0: μ = 3 years H0: μ > 3 yearsH0: μ ≥ 2.5 yearsH0: μ = 1.8 years(b) alternative hypothesis Ha: μ ≠ 2.5 yearsHa: μ > 3 years Ha: μ ≥ 1.8 yearsHa: μ ≤ 3 yearsHa: μ > 2.5 years

Answer 1

The null hypothesis is
`H_0: \mu = 2.5`.

The alternative hypothesis is
`H_1: \mu > 2.5`

Explanation:

Suppose that a recent article stated that the mean time spent in jail by a first-time convicted burglar is 2.5 years.

At the null hypothesis, we test if the mean is of 2.5 years, that is:

`H_0: \mu = 2.5`

A study was then done to see if the mean time has increased in the new century.

At the alternative hypothesis, we test if the mean has increased, that is, if it is above 2.5 years. So

`H_1: \mu > 2.5`