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# An engineering firm is evaluating their back charges. They

### Resolved Question:

An engineering firm is evaluating their back charges. They claim that their average back charge is \$1800. They randomly select 35 customers, and calculate the sample mean back charge to be \$1975. If the standard deviation of back charges is \$550, and alpha = 0.05, test the claim of the engineering firm. Perform an appropriate hypothesis test, showing the necessary calculations and/or explaining the process used to obtain the results
Submitted: 6 years ago.
Category: Math Homework
Expert:  abozer replied 6 years ago.

abozer :

Hi again,

abozer :

Ho: μ = 1800
Ha: μ ≠ 1800

abozer :

This is a two-tailed test.

abozer :

significance level = 0.05

abozer :

critical values: z = -1.96 and 1.96

abozer :

test statistic = (1975 - 1800)/(550/sqrt(35))

abozer :

= 1.882

abozer :

The test statistic is not more extreme than the critical values.

abozer :

So we cannot reject the null hypothesis.

abozer :

We don't have sufficient evidence to conclude that the average back charge is different than \$1800.

abozer :

Please let me know if you have any questions.

JACUSTOMER-7yewrnq3- :

I'm still trying to work it out.....

abozer :

do you have any questions?

JACUSTOMER-7yewrnq3- :

I got It!!!!!! Thanks for all you help