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

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

Step-by-step 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.

b

step-by-step explanation:

a difference is the result of subtraction. while each of these expressions has subtraction in it, a difference will be the result when subtraction is the last operation applied in the order of operations for the expression. this means subtraction must be outside of the parenthesis. only b has this.