A random sample of 54 students from Cabrillo College are selected from a normal population with mu equal to 20 and sigma equal to 5. After a treatment is administered to the students, the researcher calculated the sample mean to be 21. Is there enough evidence to conclude that the treatment had an effect at the 5% significance level?  If the z-statistic equals 1.46 and the critical values are -1.96 and 1.96, what conclusion can we make?   (a)reject the null hypothesis and accept the alternative hypothesis (b)cannot determine (c)fail to reject the null hypothesis (d)fail to reject the alternative hypothesis

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