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psy1205: introduction to statistics > idk > Flashcards

idk Flashcards

1
Q

what is the multiplicative law?

A

probability of a set of independant events all happeing is the product of the individual probabilities

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2
Q

what does the combination rule do

A

work out the chances of picking ‘r’ things out of N things

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3
Q

what are the steps for wilcoxon rank sum?

A
  1. rank data with both groups in one (but note which comes from which group)
  2. calc sum of ranks of group with smaller sample (if equal sample, lower sum of ranks)
  3. significant if W is smaller or equal to value in table.
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4
Q

where is Wilcoxon ranks sum in the decision tree?

A 
continuous data
more than one participant
comparing central tendency
unrelated sample (two separate groups)
NOT both normal and variance equal
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5
Q

what is Wilcoxon rank sum test basically trying to find out?

A

how much two groups overlap

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6
Q

what are the steps for wilcoxon matched pairs?

A
  1. calc difference between each pair (remove those w no diff)
  2. rank differences, ignoring sign!
  3. calculate sum of pos diffs and neg diffs
  4. t= smaller of two ranks youve calculated
  5. significant if T is smaller or equal to value in table
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7
Q

how do you do a normality check for related samples

A

use the differences (doesnt matter what way round you subtract)

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8
Q

what are the steps of the binomial test?

A

that formula that goes a little something like:

prob(x) = N! / x! (N-x)! * P^xQ ^(N-x)

significant if its smaller/ equal to

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9
Q

in the binomial test, what is base rate?

A

used to describe the percentage of a population that demonstrates some characteristic (p and q part of formula i think)

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10
Q

what are the steps for the n-by-1 chi square test?

A
  1. calculate expected value (mean of observed values) THINK THIS IS ONLY IF THERES ONE ROW. IF NOT, (row total x column total)/grand total
  2. O - E
  3. square these
  4. divide these by E
  5. sum of these. gives us x^2 value
  6. calculate degrees of freedom (N-1)
  7. significant if higher
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11
Q

what are the steps for chi-square contingency?

A
  1. calculate expected value (row total x column total)/grand total

then same as n-by-1 chi square!!!

  1. O - E
  2. square these
  3. divide these by E
  4. sum of these. gives us x^2 value
  5. HOWEVER, degree of freedom is (row-1) x (column-1)
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12
Q

what must you remember about chi square test and one/two tailed?

A

chi-square will always be two tailed

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13
Q

what must you remember about chi square test and expected values

A

the calculation of chi-square assumes all expected values are at least 5. if not, the significance may be invalid because it leads to a loss of power aka harder to find significant test.

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14
Q

what are the steps of the variance test?

A
  1. calculate variance for each group using formula
  2. homogeneity of variance- do groups differ significance in variance?? divide larger v by smaller v (use formula). gives F value.
  3. significant if F exceeds value in table
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15
Q

what are the steps of the z test?

A
  1. calculate z using formula which is:

observed value- population mean / population standard deviation

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16
Q

what is the z-test used for?

A

used to see if 1 person mean is same/diff to population mean

17
Q

whats that confusing thing that you have to remember for the z-test?

A

be careful of the question.
if its something like “what proportion of population are scoring LOWER than person” or “HIGHER” then use table score.

but if its “is this person diff from population as a whole” then DOUBLE SCORE to consider people higher and lower.

18
Q

what is exploratory data analysis?

A

idfk

19
Q

how can the unrelated sample t-test be split

A

equal sample and unequal sample size

20
Q

how do you know whether to do wilcoxon rank sum or unrelated t-test?

A
  1. normality check
  2. calc variance for each group

no sig. diff = t-test
sig diff = wilcoxon

21
Q

what are the steps for the unrelated samples t-test with EQUAL sample sizes

A
  1. calculate differences between means
  2. calulate standard error using formula
  3. calculate t statistic using formula
  4. calculate d.f. (2N-2)
  5. significant if it exceeds
22
Q

what are the steps for the unrelated samples t-test with UNEQUAL sample sizes

A
  1. calculate the pooled variance estimate using formula
  2. use pooled variance estimate to calculate standard error using formula
  3. calculate t as before using pooled variance estimate standard error
  4. calculate d.f. (N1 + N2 - 2)
23
Q

which are the tests which measure amount of overlap and tell you likelihood this happened by chance

A

related + unrelated t-tests, and z-test

24
Q

of the question says “significantly higher / lower” what is it measuring?

A

central tendency

25
Q

what are the steps of the Pearson test?

A
  1. calculate standard deviation for X and Y using formula
  2. also calculate the covariance using formula
  3. using the standard deviations and covariance, calculate Pearson product moment (r) using formula
  4. significant if r exceeds value in table
26
Q

when do you know to use spearmans instead of pearsons?

A

if its not normal

or less than 10 in sample

27
Q

what are the steps of spearmans test?

A
  1. rank each group separately

THEN USE EXACT SAME METHOD AS PEARSONS BUT USING RANK DATA RATHER THAN RAW DATA

  1. calculate standard deviation for X and Y using formula
  2. also calculate the covariance using formula
  3. using the standard deviations and covariance, calculate Pearson product moment (r) using formula
  4. significant if r exceeds value in table
28
Q

when is a normality check EDA used?

A

t test or pearsons

29
Q

when is a variance test EDA used?

A

unrelated t-test

30
Q

what are the steps for related t test?

A
  1. take differences (and ensure data is normally distributed)
  2. calculate mean (dont remove 0’s!!)
  3. calculate s.d. of differences suing formula
  4. using the s.d., calculate the standard error using formula
  5. divide mean difference by standard error (t)
  6. calculate d.f. (N-1)
  7. significant if t exceeds

psy1205: introduction to statistics (1 decks)

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