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T-tests Flashcards

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1
Q

In a dependent sample t-test, what is the first step?

A

Find the research and the null hypothesis in words and symbols

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2
Q

In a dependent means t-test, what is step 2?

A

Determine the characteristics of the comparison distribution

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3
Q

What are the characteristics of a comparison distribution?

A

Mean
Standard deviation
Shape

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4
Q

What is the comparison distribution for a dependant means t-test?

A

Distribution of means of difference scores

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5
Q

What is the mean in a dependent means t-test?

A

Mew sub M = Mew

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6
Q

How to find standard deviation in dependent means t-test

A

S^2 = SS / N-1
S = square root of S^2
SM = S / square root of N

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7
Q

What is the shape in a dependent means t-test?

A

A t-distribution with N-1 degrees of freedom

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8
Q

What is step three of dependent means t-test?

A

Determine the cutoff score on the comparison distribution

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9
Q

How to find the cutoff score on the comparison distribution table

A

Go to the column of the df (N-1)
Go to the row of alpha (assume .05 if not given)
Find matching cutoff score

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10
Q

What is step four of dependent means t-test?

A

Determine the score of your sample on the comparison distribution of the means of difference scores
Find t

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11
Q

How to solve for t

A

t = M - mewM / SM

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12
Q

What is step 5 of dependent means t-test?

A

Determine whether or not to reject the null
- if the score of your sample falls further than the cutoff score then you reject the null.

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13
Q

Step one of single sample t-test

A

State the populations and a research and null hypothesis as words and symbols

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14
Q

Symbol version of population one

A

Mew 1

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15
Q

Mew 1 in words

A

Population one

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16
Q

Population two as symbols

A

Mew 2

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17
Q

Mew 2 as words

A

Population two

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18
Q

Null hypothesis for a single sample t-test

A

Mew 1 = Mew 2

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19
Q

What does the population 1 consist of in a single sample t-test?

A

The population being studied

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20
Q

What does the population 2 consist of in a single sample t-test

A

The general population

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21
Q

Research hypothesis in single sample t-test

A

Mew 1 does not equal Mew 2

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22
Q

What is step two in a single sample t-test?

A

Determine the characteristics of the comparison distribution

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23
Q

What are the characteristics of a comparison distribution in a single sample t-test?

A

Mean
Standard deviation
Shape

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24
Q

What is the comparison distribution for a single sample t-test?

A

Distribution of means

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25
Q

When you have 2 sets of means for each person in a dependent means t-test, what should you do?

A

Combine the means to make a difference score for each person

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26
Q

How to calculate a difference score for a dependent means t-test

A

Score 2 - score 1 (after - before)
Mean of difference scores = MD

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27
Q

How to calculate deviation for a dependent means t-test

A

D - MD
Difference score - the mean of difference scores

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28
Q

How to calculate squared deviation in a dependent means t-test

A

Square the deviation in the previous column
SSD = sum of squares D

29
Q

How to find SSD (Sum of Squares D)

A

Add together all of the squared deviations

30
Q

What is the research hypothesis for a dependent means t-test?

A

Research shows an increase = Mew after - Mew before > 0
- difference scores are greater than 0

31
Q

What is the null hypothesis for a dependent means t-test?

A

The mean of the population of difference scores = 0
- no difference
- or an effect in the opposite direction of the research hypothesis

32
Q

What is the mean symbol in a single sample t-test?

A

Mew sub M
= Mew

33
Q

Calculate standard deviation in a single sample t-test

A

USE SAMPLE VARIANCE WHEN POPULATION VARIANCE ISN’T GIVEN!
Sigma sub M = sigma / square root of N
OR
SD^2 = SS / N
OR
S^2 = SS / N - 1 or SS / df

34
Q

Formula for estimated population variance

A

S^2 = SS / N-1

35
Q

Estimate of the population standard deviation

A

S = square root of S^2

36
Q

Estimated standard deviation of the distribution of means

A

SM = S / square root of N

37
Q

What is the shape of the comparison distribution in a single sample t-test?

A

T-distribution with N-1 df

38
Q

T-distribution

A

When the df is higher, the distribution shape looks more normal
When the df is lower, the distribution shape looks more heavy tailed

39
Q

Step three of single sample t-test

A

Determine the cutoff sample score using a t table

40
Q

Step four of single sample t-test

A

Determine where the sample score falls on the comparison distribution
- goes on each side of the curve

41
Q

How to find t for a single sample t-test

A

t = ( M - Mew sub M ) / SM

42
Q

In a single sample t-test, which side of the curve do we put the cutoff score?

A

Both sides (one negative and one positive)

43
Q

Step five of single sample t-test

A

Decide whether or not to reject the null

44
Q

How do you know to reject the null in a single sample t-test?

A

If the sample score is different to the cut off score

45
Q

What is the comparison distribution for a t-test for independent means?

A

A distribution of differences between means

46
Q

How to calculate comparison distribution for a independent means t-test

A

Take the mean of the experimental groups distribution of means
Take the mean of the control groups distribution of means
Subtract the control group from experimental group to get difference between means

47
Q

Three characteristics of a comparison distribution in independent means t-test

A

Mean
Shape
Standard deviation

48
Q

Find the mean in an independent means t-test

A

Mew M1-M2 = 0

49
Q

Find the shape of the comparison distribution for an independent means t-test

A

T-distribution with df total

50
Q

How to calculate df total

A

df total = df1 + df2
- df1 = N1-1
- df2 = N2-1

51
Q

What is the standard deviation for an independent means t-test

A

Standard deviation = Sdifference

52
Q

Sdifference
Independent means t-test

A
  1. S1^2 = SS1 / N1-1 and S2^2 = SS2 / N2-1
  2. S^2pooled = [df1 / df total (S1^2) ]+[df2 / df total (S2^2) ]
  3. SM1^2 = S^2pooled / N1 and SM2^2 = S^2pooled / N2
  4. S^2 difference = SM1^2 = SM2^2
  5. S difference = square root of S^2 difference
53
Q

If there are 10 volunteers and I randomly assign half of them to each group, what’s the N of each group?
Independent means t-test Q

A

N1 = 5
N2 = 5

54
Q

For each sample in an independent means t-test, what should I calculate?

A

The mean and the sum of squares for each

55
Q

What is population one in an independent means t-test?

A

The experimental population/ group

56
Q

What is population two in an independent means t-test?

A

The control population/ sample group

57
Q

What is the research hypothesis in an independent means t-test?

A

Pop1 < Pop2
OR
Pop1 > Pop 2

58
Q

What is the null hypothesis in an independent means t-test?

A

The opposite to the research hypothesis

59
Q

Step three of an independent means t-test

A

Find the cutoff score on the comparison distribution

60
Q

How to find the cutoff score of the comparison distribution

A

One or two tailed test?
df = ?
Alpha = ? (assume .05 if not told)

61
Q

Step four of an independent means t-test

A

Score of the sample on the comparison distribution

62
Q

Score of the sample on the comparison distribution

A

t = [(M1 - M2) / Sdifference ] - 0

63
Q

Step five of an independent means t-test

A

Decide whether to reject the null

64
Q

How do you reject the null in an independent means t-test?

A

If the sample score is more extreme than the cutoff score

65
Q

Effect size

A

The difference between the population means divided by the population’s standard deviation
d = (mew1 - mew2) / sigma

66
Q

Calculate estimated d

A

d = (mew1 - mew2) / Spooled

67
Q

Effect size conventions

A

.20 = small
.50 = medium
.80 = large

68
Q

Find power in an independent means t-test

A

Decide if it’s a one or two tailed test
Find N overall (2 groups of 5 = 10)
What is the effect size?

Psych Stats (2 decks)

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