Question

how to know exact t value using sample standard deviation and sample mean and sample size
i think df is sample size -1 .
we usually use approx value but to use exact value how to use t score table.
and how we conclude whether it is two tailed test or one tailed test .
(i f the problem asks for exact increase or decrease ,is it one tailed test ,i guess so ,)
please clarify my doubts

Answer 1

Yes, df = n-1

For two-tailed test:

Ho: mean = X
Ha: mean ≠ X

For one-tailed test:

Ho: mean < or = X
Ha: mean > X

or

Ho: mean > or = X
Ha: mean < X

Ho = null hypothesis
Ha = alternative hypothesis

Answer 2

how do we know it is one tailed test or two tailed test?

Answer 3

What are your hypotheses? That determines difference between one-tailed and two-tailed (see my previous post).

Answer 4

the average weekly earnings of a production worker were $424. to know if wages, on average, have gone up since that time. To test this, you sample 64 production workers, and determine that their average salary is $432.69, with a sample standard deviation of $33.90. Use a 0.05 level of significance .carry out test .
is it t test or z test ? how would we know

in this case one tailed or two tailed how can we know?

Answer 5

If a population proportion is 0.29 and if the sample size is 120, 25% of the time the sample proportion will be less than what value if you are taking random samples?

Round your answer to 2 decimal places, the tolerance is +/-0.01.