L12 - One and Two sample T-tests

Question 1

What does hypothesis testing do?

Answer 1

it is used to test the validity of a claim (AKA the Null Hypothesis) that is about population using sample data.

Question 2

what is a P-value

Answer 2

it is a measure of how surprising it is that the null hypothesis gets rejected as a probability.
- The lower the p-value, the more surprising the evidence is.

Question 3

what does a one sample t-test do?

Answer 3

It is a statistical hypothesis test used to determine whether an unknown population mean is different from a specified value.

Question 4

what are the required assumptions for a one sample t-test 2

Answer 4

1. The data are interval or ratio
2. The sample is drawn from a population that is normally distributed.

Question 5

What are the two things that you are comparing within a one sample t-test.

Answer 5

one will be the calculated t value from a data set. The other could be the population parameter, or a performance expectation.

Question 6

What is the equation for a one sample t-test

Answer 6

T = sample mean - comparison value
__________________________________
Standard error of the mean

Question 7

what is a sampling distribution?

Answer 7

The distribution of values taken by a statistic when one takes all possible samples of a given size from a population, and graph it

Question 8

what is the equation for the standard error of the mean

Answer 8

SE = s / n^-1

Question 9

What is the standard error of the mean?

Answer 9

It is the standard deviation of the sampling distribution.

Question 10

whats the difference between standard deviation and standard error of the mean?

Answer 10

the standard error of the mean estimates the variability between samples whereas the standard deviation measures the variability within a single sample.

Question 11

what does alpha represent?

Answer 11

significance level

Question 12

what does DF represent?

Answer 12

Degrees of freedom (n-1)

Question 13

what are three ways to test normality?

Answer 13

• histogram and box-plot
• normal probability plot
• goodness of fit test

Question 14

Draw positively skewed distribution, negatively skewed distribution and a bimodal distribution.

Answer 14

positively skewed - majority of data points closer to 0
negatively skewed - majority of points further away from zero
Bimodel - has two peaks in the dataset.

Question 15

what two variables are needed to find the critical value of T

Answer 15

Degrees of freedom and the significance level

Question 16

what does a two sample t- test do?

Answer 16

they compare two sample means so as to infer whether they are drawn from the same population.

Question 17

what is the Equation for a two sample t- test (pooled & unpooled)

Question 18

what is the difference between a pooled and and unpooled t-test

Answer 18

when the variances of the two populations are similar you should preform a pooled t test.
when the variances of the two populations are not similar you should use the unpooled t-test

Question 19

what is pooling?

Answer 19

a technique used to obtain a more accurate estimate of the standard deviation of a sample statistic by combining the estimates given by the independent samples.
the standard deviation is weighted based in the sample it represents.

Question 20

what are the 4 assumptions of a two sample t test

Answer 20

1. data are interval or ratio
   2.populations from which the samples are drawn must be normally distributed
2. samples are independent
3. the variance of the populations from which the samples are drawn are similar