statistics t test

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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 ,)

• statistics t test -

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

• statistics t test -

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

• statistics t test -

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

• statistics t test immediate help needed -

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?

• statistics t test -

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?

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