Quant Methods

Question 1

what are we asking when we use statistical inference?

Answer 1

whether the samples were generated or sampled from the same underlying population

Question 2

what is the measurement of mode?

Answer 2

the value that was recorded the most, so there can be two if two different heights were recorded the same amount of time and they were both the most frequently observed height

Question 3

how can we compute the probability of observing a specific data point?

Answer 3

by finding the area under the curve can compute the probabilities of certain regions in the distribution and then in turn apply this to a specific point

Question 4

what is a one way ANOVA? what is our goal ?

Answer 4

analysis of variance.

goal is to measure/compare data from two or more independent groups

Question 5

what is it called when we have more than two different independent groups?

Answer 5

a between subjects design

Question 6

what are we examining when we are doing in a between subjects design?

Answer 6

questioning if any of the groups significantly differ from any of the other groups and testing whether all groups were generated from the same distribution?

Question 7

within group variation occurs by; between group variation occurs by

Answer 7

variation due to random sampling; variation due to random sampling PLUS additional variance due to experimental manipulation

Question 8

what is the formula for sum of squares ?

Answer 8

SS total = Σ(x - M)^2

for all scores

Question 9

what are the steps to ANOVA analysis?

Answer 9

get the SS for the total distribution
then get the SS for each individual group (eg, students, ambos and fire fighters groups) and add these values together
then subtract the added individual group scores from the SS total
SSbetween = SStotal - SSwithin

Question 10

how do you compute variance?

Answer 10

square the SD eg SD of 1.98 squared = 3.95

Question 11

what is the relationship between the SS and variance?

Answer 11

variance is the average SS that we predict, eg, if we take the SS and divide by number of data points we have in each group (N) that equals the variance

Question 12

what is the formula to compute SSbetween?

Answer 12

[Σini(mi - M)^2]

Question 13

when will the variation of the total data when measuring variance between groups be greater?

Answer 13

when the means for each group are different

Question 14

what does the F ratio tell you?

Answer 14

what the size of the actual ANOVA is

Question 15

in regards to anova, using words, explain what the p value is telling us?

Answer 15

the probability of observing this f ratio with these degrees of freedom if there is no variation between groups (no effect)
basically, what is the probability of the data under the assumption the null hypothesis is true

Question 16

what actually is the f ratio ?

Answer 16

the variation between groups compared to ratio of variance within groups
between group variation
f = ———————————-
within group variation

Question 17

how do you compute the f ratio?

Answer 17

mean square within between groups divided by mean square within groups
MSbetween
F = ——————-
MSwithin

Question 18

why can’t we use the SS directly to compute the f ratio?

Answer 18

SS is sensitive to our sample size, so we can’t just divide the SSbetween by the SSwithin

Question 19

how do we correct the SS to compute the F ratio?

Answer 19

by dividing by the degrees of freedom (no. of independent groups, and no. of subjects)

Question 20

what does N equal?

Answer 20

total data set

Question 21

what are the 3 df that we can compute?

Answer 21

dftotal
dfbetween
dfwithin

Question 22

how do we compute df total?

Answer 22

N (no. of total subjects) minus 1

= N-1

Question 23

what does k equal?

Answer 23

number of conditions

Question 24

how do we compute df between?

Answer 24

number of conditions (k) minus 1
eg 3 conditions minus 1
= k-1

Question 25

how do we compute df within?

Answer 25

= N-k
number of participants minus number of groups
eg 3000 participants and 3 groups would mean
3000-3 = 2997

Question 26

what is the mean square within groups?

how is it calculated?

Answer 26

the measure of within groups variation that has been corrected for sample size
- SSwithin divided by dfwithin

Question 27

what is the mean square between?

Answer 27

the measure of between groups variation corrected for sample size ‘
- SSbetween divided by df between

Question 28

when do we have evidence that the difference is real when using f ratio?

Answer 28

when the f ratio is sufficiently large

as when F is large, it is very unlikely to achieve this score if the differences were due to chance alone

Question 29

how do you determine whether an f ratio is extreme or not?

Answer 29

it is assessed against the F distribution

Question 30

what do we require to tell us what the shape of the f distribution is?

Answer 30

dfwithin and dfbetween

Question 31

F ratio will always be a positive number? T or F?

Answer 31

True

Question 32

how do we compute the probability of observing an f ratio with a specific value?

Answer 32

by finding the area under the curve

Question 33

if the f ratio is greater than the value that represents the 95% cutoff, what do we do?

Answer 33

we conclude that the differences between the means of our groups is actually significant

Question 34

what does the p value tell us?

Answer 34

the probability of your f ratio assuming the null hypothesis is true?

Question 35

what is the null hypothesis?

Answer 35

is that there is no difference between the groups - that all groups were generated from the same population

Question 36

when is the p value less than 0.5 when using ANOVA?

Answer 36

when the f ratio is larger than that 95% cut off

Question 37

T or F? ANOVA tells us if there is a sig. difference, but also tells us how big the difference is (effect size)

Answer 37

False, does not tell how big the diff. is

Question 38

what are the 2 things anova does not tell us?

Answer 38

how big the difference is, and where the difference is coming from

Question 39

when would you use a two/three way ANOVA; a repeated measures ANOVA?

Answer 39

you have more than one factor which differs between groups; you have a within subjects design