Hypothesis Tests: The t-Tests

Question 1

What is a t-test

Answer 1

A statistical test that COMPARES THE MEANS OF TWO SAMPLES

Question 2

What is the Null Hypothesis?

Answer 2

The hypothesis that assumes the POPULATIONS ARE IDENTICAL

Question 3

If P<0.05

Answer 3

The results is against the null hypothesis

Question 4

If P<0.01

Answer 4

Strong evidence the result is against the null hypothesis

Question 5

If P<0.001

Answer 5

Very strong evidence the result is against the null hypothesis

Question 6

If the null hypothesis is true what is the P value

Answer 6

P>0.05

Question 7

What are the types of T-test

Answer 7

Unpaired and paired

Question 8

How is the differences in data structure of the two data sets within the t-tests reflected

Answer 8

Reflected in the SE

Question 9

What does a unpaired t test do

Answer 9

Compares two UNRELATED SAMPLES
such as a group of patients given saline or fentanyl

Question 10

What assumptions are there with an unpaired t test?

Answer 10

1. Each sample is drawn from a NORMAL POPULATION
2. POPULATIONS HAVE A COMMON STANDARD DEVIATION

Question 11

What is the null hypothesis for a unpaired t-test

Answer 11

The population means are the same

Question 12

Can you still do a unpaired t-test when the populations are NON-NORMAL but departure from NORMALITY is SLIGHT

Answer 12

Yes as the violations of the ASSUMPTIONS are usually of little consequences

Question 13

What does SDs being not equal relate to

Answer 13

The data being skewed

Question 14

What is normal distribution characterised by

Answer 14

Standard Deviation and Mean
Therefore a test that assessed equality of means and pay no attention to the standard deviation. Therefore the best estimate of population mean draws on information from both samples and is a pooled estimate

Question 15

What is a paired t test

Answer 15

Compares TWO RELATED SAMPLES

Question 16

What does the Paired t test take into account

Answer 16

The pairing by FORMING THE DIFFERENCES BETWEEN EACH PAIR. Once the differences have been formed the original observations are discarded.

Question 17

What does the paired t test anaylse

Answer 17

ONLY THE DIFFERENCES BETWEEN EACH PAIR

Question 18

How to assess whether a SINGLE SAMPLE OF DIFFERENCES COMES FROM A POPULATION WITH MEAN ZERO

Answer 18

Paired t-test

Question 19

What is SE in an unpaired t test based on

Answer 19

Standard deviation which measures the VARIATION BETWEEN the two samples

Question 20

In a paired t test the act of taking the difference between two values from related samples would it expectedly remove

Answer 20

It removes the variation of standard error between the two samples from the data

Question 21

What will pairing the data in the lead to in a paired data

Answer 21

A more sensitive experiment

Question 22

How will the advantage of pairing the data be lost

Answer 22

If it is not reflected in the arithmetic used for the data analysis

Question 23

How will the correct precision be ascribed to the difference in means in a t test

Answer 23

The correct precision can only be ascribed of the APPROPRIATE SE for the paired data is used

Question 24

What is the Assumption in Paired t test

Answer 24

1.DIFFERENCES between the two related samples have to come from a NORMAL DISTRIBUTION.

(Normality not necessary to specify the distribution of the individual observations , just there Differences)

2. MODEST departures from normality are not usually troublesome, like unpaired

Question 25

If 0 is included in a 95% confidence interval for the t-test what will the associated hypothesis test give

Answer 25

P>0.05

Question 26

If 0 is NOT included in a 95% confidence interval for the t-test what will the associated hypothesis test give

Answer 26

P <0.05

Question 27

If the null hypothesis (P>0.05) is TRUE where are the values in relation to the 95% confidence intervals

Answer 27

The values are within the 90
5 confidence interval are the values of X that are compatible with the data

Question 28

In a Paired test what does it not assume

Answer 28

1. 2 Populations
   2, Normality in each populations

Question 29

In a paired test what does it assume

Answer 29

The differences are normally distributed

Question 30

In a unpaired t test what does it assume

Answer 30

1. The two populations are normal
   2, Has a common standard deviation but does not assume eqaulity of SD estimates from the two samples