Which of the following is a major difference between a hypothesis test with the t statistic formula and the test with a z‐
score?
a) You must know the population variance (or standard
deviation) for the z‐score but not for the t statistic.
b) You use the unit normal table to find critical values for
the z‐score test but not for the t test.
c) You must calculate the sample variance (or standard
deviation) for the t statistic but not for the z‐score.
d) All of the other options are major differences.

What's the key difference between the t- and z-distributions? The standard normal or z-distribution assumes that you know the population standard deviation. The t-distribution is based on the sample standard deviation.

5=812a+9+3

step 1: simplify both sides of the equation.

5=812a+9+3

5=(812a)+(9+3)(combine like terms)

5=812a+12

5=812a+12

step 2: flip the equation.

812a+12=5

step 3: subtract 12 from both sides.

812a+12−12=5−12

812a=−7

step 4: divide both sides by 812.

812a /812 = -7/812

a= -1/116

so the answer is

a=   -1/116