Statistics

Question 1

what issue do stats mainly serve to solve?

Answer 1

to workout the likelihood that the results were obtain by chance

Question 2

what shape is the probability distribution

Answer 2

bell curve

Question 3

what does the null hypothesis help to determine?

what does it assume?

Answer 3

how unlikely our empirical result was under the chance distribution
null hypothesis assumes that result was all due to chance

Question 4

what can we use to represent the chance distribution?

Answer 4

t-distribution and z-distribution

Question 5

when can we only use z distribution?

Answer 5

when we know the population standard deviation

Question 6

what is used when you do not know the population standard deviation?

Answer 6

t-distribution

Question 7

what do you calculate the empirical t value

Answer 7

you take the difference between the observed mean, and the population mean, and divide it by the standard error of the mean

Question 8

what is the population mean under the null hypothesis ?

Answer 8

zero

Question 9

what changes the shape of the t distribution?

Answer 9

the degrees of freedom

Question 10

smaller degrees of freedom change the shape of the t distribution by in what way?

Answer 10

the smaller the df, the “fatter” the tails will be, meaning more results cam call under this

Question 11

….

Answer 11

the the observed t value, given the null hypothesis that t=0

Question 12

what does a one sample design involve ?

Answer 12

comparing group data to known values (like IQ or “an hour” waiting time)

Question 13

what is another name for a between groups design ?

Answer 13

an independent measures design

Question 14

independent samples t test is used for…?

Answer 14

independent measures design

Question 15

what is the main benefit of using an independent measures design

Answer 15

there will be no learning effects due to repeated exposure

Question 16

what is the main 2 disadvantages of independent measures design?

Answer 16

• people in different groups might greatly vary

- we cannot study how things can change overtime

Question 17

what is another name for the within group design?

Answer 17

repeated measure design

Question 18

what are 2 main advantages of repeated measures designs?

Answer 18

baseline factors like personality etc don’t have to be accounted for as they will affect both conditions equally
- can study changes in behaviour over time

Question 19

what are 2 main disadvantages of repeated measures designs?

Answer 19

• measurements are not independent
• people cannot be naive in second round
• need to factor in order effects (who does what condition first or second)

Question 20

what is the one sample t test formula?

Answer 20

M - u
t = ________

 S subscript M

Question 21

what is the formula to work out the standard error of the mean?

Answer 21

S
S (subscript) m = _______
square root
of n

Question 22

the standard deviation is what? how is it represented in formulas?

Answer 22

the square root of the variance

S

Question 23

how do we get the variance number?

Answer 23

the sum of squared differences divided by degrees of freedom

Question 24

why do we square the final value?

Answer 24

because we care about the magnitude not whether or not its above or below the mean

Question 25

t or f. the t value also quantifies the effect and tells us how strong the effect is

Answer 25

false

Question 26

what is the standard deviation formula?

Answer 26

SS
s^2= _____
df

then square root this number

Question 27

what is the t equation for the independent measures t test?

Answer 27

(Ma-Mb)-(ua-ub)
t= _____________
S subscript
(Ma-Mb)

Question 28

what is S

(Ma-Mb)

Answer 28

the difference between two means

standard error of the mean difference

Question 29

what is a key component of working out the standard error of the mean difference?

Answer 29

the pooled variance

Question 30

how do you calculate the pooled variance?

how does this look in a formula?

Answer 30

summing up the summed squared differences (SS) from each condition and dividing it by the sum of the df
SSa + SSb
s2p = ___________
df a + df b

Question 31

what is the short hand for pooled variance?

Answer 31

2
S
p

Question 32

the pooled variance is just what?

Answer 32

the average of the two sample variances

Question 33

what mean do we need to acquire in a paired samples t test ?

Answer 33

the difference mean
so we subtract the result from condition b from the result of condition a for all participants, and then find the mean of all these differences

Question 34

true or false, cohen’s d gives an estimate of effect size that is independent of sample size

Answer 34

true

Question 35

what does the d refer to in cohen’s d?

Answer 35

the mean difference divided by the standard deviation

Question 36

what are the conventional cut offs varying sizes in cohen’s d result?

Answer 36

small: 0.2-0.5
medium: 0.5 - 0.8
large: greater than 0.8

Question 37

what does r^squared mean?

Answer 37

variance explained

Question 38

True or false, r^2 is dependent on the sample size

Answer 38

true

Question 39

what is the formula for r^2

Answer 39

t^2
r^2= _______
t^2 +df

Question 40

what are the conventional cut offs of varying sizes in r^2

Answer 40

small: 0.01 - 0.09
medium: 0.09 - 0.25
large: bigger than 0.25

Question 41

what is a confidence interval?

Answer 41

setting parameters based on the assumption that the sample mean should be relatively near to the corresponding population parameter