Central Tendancy + Effect Size - Week Two

Question 1

Define trimmed mean

Answer 1

A measure of central tendency that disregards proportion of scores at either end of the distribution and then calculates the mean

Eg. 10% = remove one num, 30% remove 3 numd

Question 2

When are mean, median, and mode equal

Answer 2

• When a symmetrical measure occurs
• When right/left skew, mean pulled in direction of skew

Question 3

How are appropriate measures decided upon

Answer 3

• Based on variables and judgements
• Data can be misleading

Question 4

How do we measure variance?

Answer 4

Through Standard Deviation and Variance

Question 5

Equation of variance

Answer 5

S^2 = sum of ( x - mean) squared
—————————————
N

1. Subtract mean from each score
2. Square each deviation
3. Add up all of deviation squared
4. Divide by num of scores

Question 6

Equation of standard deviation

Answer 6

SD = Square root of S^2

Question 7

How can you estimate standard deviation from a histogram?

Answer 7

-1SD (between start and mean)
M
+1SD (between mean and end)

Question 8

What is the equation for Z-Score and define it

Answer 8

• Issues with raw score so allows for standardisation
• Number of SD a raw score is above/below mean
  M = 0. SD=1

Z = X-M
——-
SD

Question 9

How can we calculate the raw score from the Z-Score

Answer 9

X = SD + Mean

(X= Raw Score)

Question 10

What is Cohen’s D used for and what is the equation?

Answer 10

• Uses standard currency to express magnitude of effect
• Allows for communication of results of two groups with different measures

Cohen’s D = U1 - U2
————-
O

(U1U2= population, O= pooled pop of SD)

Question 11

What values define small, medium, and large effects using Cohen D

Answer 11

D = 0.2 Mean> 59.9% of control
D= 0.5. Mean > 69.2% of control
D= 0.8. Mean > 78.8% of control

Question 12

Values of small, medium, and large effects using Partial Eta Squared

Answer 12

n^2 = 0.01
N^2= 0.06
N^2= 0.8