How do you find P value with unknown standard deviation?
Having less data and/or not knowing the population standard deviation should create a higher burden of proof. is unknown, you estimate it with s, the sample standard deviation.) This is a job for the t-test. To calculate the p-value, you look in the row in the t-table for df = 9.
Which procedure is appropriate when σ is unknown?
hypothesis test
A hypothesis test for a population mean when the population standard deviation, σ, is unknown is conducted in the same way as if the population standard deviation is known. The only difference is that the t-distribution is invoked, instead of the standard normal distribution (z-distribution).
When is the value of the standard deviation unknown?
What they are talking about is the value of the standard deviation. When the value is assumed to be known you can divide the sample mean by it and if the samples have a normal distribution the sample mean minus the population mean divided by the “known” standard deviation divided by the square root of the sample size n has a standard normal
What to do when the population variance is unknown?
So when the population variance is unknown the t distribution is used to construct confidence intervals for the population mean. The standard error of the mean is the sample standard deviation divided by the square root of n.
How to compare two independent populations with unknown standard deviations?
The test comparing two independent population means with unknown and possibly unequal population standard deviations is called the Aspin-Welch t-test. The degrees of freedom formula was developed by Aspin-Welch.
Do you use the standard deviation of the sample?
In this case, we need to use the standard deviation of the sample (s) to estimate the standard deviation of the population (σ). Because of this estimation, we need to use the t-distribution, instead of the z-distribution to make our comparison.