Circle the best answer. the choice between a z-test and a t-test for a population mean depends primarily on: a. the sample size. b. the level of significance. c. whether a one- or two-tailed test is indicated. d. whether the given standard deviation is from the population or the sample. e. a z-test should never be used. 3

a)The sample size

Step-by-step explanation:

t - student distribution should be used whe we are facing a Normal Distribution population andwhen a sample size n is below 30.

t- student distribution is also a associated to a bell shape but is more flat and the values are more spread, tails are much more wide.

t- student use the concept of degree of fredom ( each degree of fredom correspont to an specific curve). As degree of fredom increase the curves become more close to a bell shape. For  n = 30 t-student curve is  a bell shape one

y=x+9

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step-by-step explanation: