Question

In a study of parents' perceptions of their children's size, researchers asked parents to estimate their youngest child's height. The researchers hypothesize that parents tend to underestimate their youngest child's size because the youngest child is the baby of the family and all other family members appear larger compared to the baby. The sample of 39 parents who were surveyed underestimated their youngest child's height by 7.5 cm on average; the standard deviation for the difference in actual heights and estimated heights was 7.2 cm, and the data were approximately normal.

Determine the TS and p-value for this study.

Answer 1

Test statistic t=6.505

P-value=0

Explanation:

This is a hypothesis test for the population mean.

The claim is that parents tend to underestimate their youngest child's size.

Then, the null and alternative hypothesis are:

`H_0: \mu=0\\\\H_a:\mu> 0`

The significance level is assumed to be 0.05.

The sample has a size n=39.

The sample mean is M=7.5.

As the standard deviation of the population is not known, we estimate it with the sample standard deviation, that has a value of s=7.2.

The estimated standard error of the mean is computed using the formula:

`s_M=(s)/(√(n))=(7.2)/(√(39))=1.153`

Then, we can calculate the t-statistic as:

`t=(M-\mu)/(s/√(n))=(7.5-0)/(1.153)=(7.5)/(1.153)=6.505`

The degrees of freedom for this sample size are:

`df=n-1=39-1=38`

This test is a right-tailed test, with 38 degrees of freedom and t=6.505, so the P-value for this test is calculated as (using a t-table):

`P-value=P(t>6.505)=0`

As the P-value (0) is smaller than the significance level (0.05), the effect is significant.

The null hypothesis is rejected.

There is enough evidence to support the claim that parents tend to underestimate their youngest child's size.