Question

The box fill weight of Frosted Flakes breakfast cereal follows a normal distribution with a mean of 9.75 ounces and a standard deviation of 0.27 ounces. A sample of 25 boxes filled this morning showed a mean of 9.85 ounces. At the 0.05 significance level, can we conclude that the mean weight is more than 9.75 ounces per box

Answer 1

Since the calculated value of z= 0.0185 does not lie in the critical region we conclude that the mean weight is less and equal to 9.75 ounces per box and accept the null hypothesis.

Explanation:

Let the null and alternate hypothesis be

H0: u ≤ 9.75 against the claim Ha: u > 9.75

Here

Population mean= u= 9.75

Standard deviation= 0.27 ounces

Sample mean= x`= 9.85

Significance level
`\alpha`= 0.05

Using z- test

z= x`-u/s/√n

z= 9.85-9.75/0.27/√25

z= 0.1/5.4

z= 0.0185

The critical region for 1 tailed test at 0.05= z > ±1.645

Since the calculated value of z= 0.0185 does not lie in the critical region we conclude that the mean weight is less and equal to 9.75 ounces per box and accept the null hypothesis.