Question

A sample of 25 one-year-old girls had a mean weight of 24.1 pounds with a standard deviation of pounds. Assume that the population of weights is normally distributed. A pediatrician claims that the standard deviation of the weights of one-year-old girls is less than pounds. Do the data provide convincing evidence that the pediatrician's claim is true

Answer 1

Paedtricians claim isn't true.

Explanation:

The hypothesis :

H0 : σ = 7

H0 : σ > 7

The test statistic ; χ² :

χ² = [(n - 1) * s²] ÷ σ²

n = 25 ; s = 4.3, σ = 7

χ² = [(25 - 1) * 4.3²] ÷ 7²

χ² = [(24 * 4.3²] ÷ 49

χ² = 443.76 / 49

χ² = 9.056

At α = 0.01 ; critical value = 42.980

Since critical value > test statistic, we fail to reject the null, H0.