Question

Our environment is very sensitive to the amount of ozone in the upper atmosphere. The level of ozone normally found is 6.8 parts/million (ppm). A researcher believes that the current ozone level is at an insufficient level. The mean of 10 samples is 6.4 ppm with a standard deviation of 1.1. Does the data support the claim at the 0.05 level

Answer 1

The test statistics fall in the critical region and hence null hypothesis is to be rejected.

Explanation:

The null hypothesis : H0 : Mean = 6.80

Alternative hypothesis: Ha: Mean is not equal to 6.80

As per the z statistics

z = (x’-mean)/(sigma/sqrt n)

Substituting the given values, we get –

z = 6.4-6.8/(1.1/sqrt 10)

z = -1.149

z test statistics is -1.149

Critical value for two tailed test at 98% confidence is .10749

The test statistics fall in the critical region and hence null hypothesis is to be rejected.