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Find Critical Z Value Assuming Normal Distribution

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Please help me solve the following, I need the steps so that I can do them myself. Let me know how many credits will be required.

1.)Find the critical z value, assume that the normal distribution applies.
alpha = 0.005; H1 is p not equal 0.20

2.)In 1990, 5.8% of job applicants who were tested for drugs failed the test. At the 0.01 significance level, test the claim that the failure rate is now lower if a simple random sample of 1520 current job applicants results in 58 failures. Does the result suggest that fewer job applicants now use drugs?

3.) Claim: The mean life span of desktop PC's is less than 7 years. Sample data: n=21, mean of the value = 6.8 years, s = 2.4 years. The significance level is alpha = 0.05.
Find the null and alternative hypothesis, test statistic, critical value, and state the final conclusion. Assume that a simple random sample has been selected from a normally distributed population

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Attached in Word and Excel are files to show how to find test statistics, null hypothesis and conclusions.

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