Question 1142943: In order to find a t-value separating the confidence interval we need to know:
Sample size and confidence level
Confidence Level and sample mean
Sample mean and sample standard deviation
Confidence Level and z-score
Answer by Theo(13342)   (Show Source):
You can put this solution on YOUR website! i think you will need the sample size and the confidence level.
the confidence level tells you how wide the confidence interval is.
for example, if the confidence level is .9, then you will need to find the t-score corresponding to an area to the left of it of .05 and the t-score corresponding to an area to the left of it of .95.
once you find that, you can find the area between those t-scores.
in order to find the t-score, however, you will also need to find the sample size.
from the sample size, you can get the degrees of freedom.
the degrees of freedom is equal to the sample size minus 1.
for example:
assume the confidence level is 90% = .9
that give you an alpha of 1 - .9 = .1.
this alpha is split between the left hand side of the confidence interval and the right hand side of the confidence interval.
assume the sample size is 30.
the degrees of freedom become 29.
you look in the t-score table for a two tail alpha of .10, which corresponds to a one tail alpha of .05.
you then look down the table for 29 degrees of freedom and the table tells you that the t-score corresponding to that would be equal to plus or minue 1.699.
you can also use a t-score calculator to get the same thing.
the table i used can be found at http://www.ttable.org/
the t-score calculator i used can be found at https://goodcalculators.com/student-t-value-calculator/
the t-score graph generator i used can be found at https://mathcracker.com/t-distribution-graph-generator.php#results
i also used the TI-84 Plus calculator which told me that the critical t-scores needed to be plus or minus 1.699126996.
those t-scores more detailed than the rounded results from the table and frm the online calculator.
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