It is claimed that the mean tenure for a chief executive office (CEO) was at least nine years. A survey of companies found a sample mean tenure of x = 7.25 years for CEOs of 90 companies with a standard deviation of s = 6.5 years. a). Provide null and alternative hypotheses. Compute the test statistic. Determine the p-value, and at 99% confidence, test the validity of the claim. b). Using the critical value approach, at 99% confidence, test the hypotheses. Based on critical value, write your conclusion

I need to know how do we calculate critical value