research skills 10 - students T test

Question 1

when is the T test used ?

Answer 1

• to compare the means of 2 groups

Question 2

what are the types of T test ?

Answer 2

standard - independent sample groups eg control vs treated
paired - take 1 sample and measure before and after effect

Question 3

what are the assumptions of the T test ?

Answer 3

• data needs to be normally distributed
• approx equal numbers in the samples

Question 4

what are the steps in the T test ? ( standard)

Answer 4

• decide on error - normally 0.05 (95%)
• identify research question
• calculate T score
• calculate degree of freedom
• look up in table

Question 5

how is the degree of freedom calculated ?

Answer 5

for a test with 2 groups degree of freedom = 2n - 2

Question 6

when can we reject the null ?

Answer 6

if the t statistic is LARGER than the critical value found in the table

Question 7

what is a one tailed or two tailed hypothesis ?

Answer 7

one tail - directional choice - only one possibility
two tailed - allow for the possibility that the test statistic is very large or very small

Question 8

how do you do a paired t test ?

Answer 8

• decide error
• form hypothesis
• find difference between each paired sample and calculate mean of all to get just once value
• calculate standard deviation
• put numbers into equation
• calculate degree of freedom ( number of pairs - 1 )
• use table