please help if you can

1. Why is the standard error of the mean used for the t-test and not the standard deviation?

• because information about the population is known and using the SD might create a unbiased result
• because information about the population is not known and using the SD might create a biased result
• because information about the sample is not known and using the SEM might create a biased result
• because information about the sample is not known and using the SD might create a unbiased result

2. What does the value of t represent?

• gives us a measure of the magnitude of the mean differences
• gives us a measure of variance
• gives us a measure of range

3. A meteorologist wants to know how the current year's amount of snowfall has compared to previous years' average snowfalls. The average snowfall is 2inches per year with a standard error of the mean of 1 inch, and this year's current snowfall was 2. Compute the one-samplet-test using these data. Please answer using whole numbers only.

4. What is the critical value of a two-tailed t-test with a degree of freedom of df=15 and using an alpha level of .01. Fill in the blank with the probability rounded to the nearest hundredth (ex: 5.24).