T-statistics

Question 1

What are t-tests?

Answer 1

Compares the means of two groups on a given variable
- Related t-test
- Independent samples t-test

Question 2

Related t-test

Answer 2

• Two groups, paired with each other
  With themselves (two different times) or a partner
• To reduce error in the outcome variable
• Compare the means between the groups; is there a difference and is the difference significant?
• Compare obtained t-value against the maximum we would expect to get if null hypotheseis were true
• Critical t-value

Question 3

Related t-test - Example

Answer 3

• 10 couples
• Measuring marriage satisfaction

Question 4

Related t-test - APA style

Answer 4

• t-value (n-1); x,yz, p<=> 0.05

Question 5

Related t-test - Tables of interesst

Answer 5

• Paired samles statistics
  Mean, N, SD
• Paired Difference Test
  Mean of difference, SD of difference scores, confidence interval , last 3 columns check if the test is significant or not

Question 6

Independent t-test - When to use it

Answer 6

• Compare means of two independent groups
  Males vs Females
  Control vs Experimental
  Students different countries
  Not related to each other
• One given variable

Question 7

Independent t-test - Example

Answer 7

• Sweden participants vs Norway participants
• Immigrants making a country better or worse

Question 8

Independent t-test - Tables of Interest SPSS

Answer 8

• Group statistics
  Mean scores
• Independent test (Table 2)
  First two columns; Homogeneity of varience
  The 3 columns after; whether the test is significant or not

Question 9

Independent t-test - APA style

Answer 9

• Look at t-value, N value, p-value, M in different groups, SD and Cohen’s d.

Question 10

Cohen-s d Values

Answer 10

• Small effect .2
• Medium effect .5
• Large effect .8

Question 11

What is confidence interval?

Answer 11

If mean of difference is between the confidence interval, it means that the difference i s plausible