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psych stats (300) > Variables & descriptive stats > Flashcards

Variables & descriptive stats Flashcards

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1
Q

Descriptive stats? (def, includes what things)

A
  • Summarize or describe data from a particular sample
  • Includes…
    –> CT: mean, median, mode
    –> SD: s, s hat
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2
Q

Inferential Stats? (def, includes what things)

A
  • Infers from the data to draw a conclusion about the pop
  • Includes…
    –> T-test
    –> Df
    –> P
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3
Q

Characteristics of a true experiment?

A
  • IV was actually manipulated by the researchers
  • DV gets measured
  • Usually involves random assignment
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4
Q

Between-groups design meaning? Ex?

A
  • Participants only see ONE condition
  • diff people in conditions, compare between them
  • EX –> drug studies
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5
Q

Within-groups design meaning? Ex?

A
  • all participants see BOTH conditions
  • same participants in both conditions, make comparisons WITHIN the group
  • EX. –> sleep study with cued & non-cued questions
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6
Q

Factors that effect between/within groups design?

A

Between:
- both conditions would give away the goal / design of study
- both conditions is impractical / impossible

Within:
- advantage b/c participants are their own comparison group

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7
Q

Operational definition? (def & ex)

A
  • how the researcher chooses to measure or manipulate variables of interest
  • Ex. they define the DV of “wellbeing” as the avg score on 2 different questionnaires
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8
Q

Discrete def? Ex?

A
  • Specific values
  • Whole numbers
  • Can’t have partial units

Ex:
- shoe size, number of people, number of legs

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9
Q

Continuous def? Ex?

A
  • full range of values
  • includes decimals

Ex:
- height, weight exam scores with partial credit

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10
Q

4 diff levels of measurement? (in order)

A
  • Nominal
  • Ordinal
  • Scale
    –> Interval
    –> Ratio
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11
Q

Nominal: memory cue, definition, Cont vs Disc, CT measures, & examples

A
  • Nom = NAME
  • Def: measured category or name
  • Always discrete
  • ONLY mode
  • Fav color, major, etc
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12
Q

Ordinal: memory cue, definition, Cont vs Disc, CT measures, & examples

A
  • Ord = ORDER
  • ordered descriptions, rankings
    –> categories, with some inherent order, but not evenly spaced
  • Always discrete
  • Mode or median (never mean)
  • 1st/2nd/3rd, Yes/maybe/no
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13
Q

Interval: memory cue, definition, Cont vs Disc, CT measures, & examples

A
  • numbers are evenly spaced, but no meaningful zero
  • often continuous
  • M, median, mode –> all good
  • IQ tests, Celsius/Fahrenheit, strongly agree/disagree questions
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14
Q

Ratio: memory cue, definition, Cont vs Disc, CT measures, & examples

A
  • ratiO –> 0
  • numbers equally spaced, have a meaningful zero point
  • often continuous
  • M, median, mode –> all good
  • reaction time, counting
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15
Q

Scale def? CT measures?

A

Includes interval and ratio level of measurement

M, med, mode –> all good

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16
Q

Mean: what is it & what is it appropriate for (variable type and distribution type/ skew/ outliers)

A
  • average –> (sum of x)/n
  • use for scale variables
  • NOT great for skewed distributions or many outliers
17
Q

Median: what is it & what is it appropriate for (variable type and distribution type/ skew/ outliers)

A
  • middle (50th %ile) of the data
  • (N+1) / 2
  • okay for ordinal & scale variables
  • okay for any distribution type
18
Q

Mode: what is it & what is it appropriate for (variable type and distribution type/ skew/ outliers)

A
  • score that occurs most often
  • okay for all variable & distribution types
19
Q

Range: what is it?

A
  • max - min scores
20
Q

IQR: what is it? how to calculate it? comparison to range & SD

A
  • contains middle 50%
  • 75%ile - 25%ile
  • better than range, worse than SD
21
Q

Variance: what is it? how to calculate it? units?

A
  • sum of squared deviations from the mean divided by the number of scores
  • Σ(x-M)^2 / N
  • Units: squared units
    lowkey useless
22
Q

Standard deviation: what is it? how to calculate it? what version does jasp give?
(don’t talk about all the diff symbols yet)

A
  • variation from the mean in standard units
  • sq root of Σ(x-M)^2 / N
  • JASP gives est. pop SD always
23
Q

Sample standard deviation is NOT a good estimate for population. It is always too ____ and is strongly effected by ____.

A

It is always too small
It is strongly effected by sample size

24
Q

Standard deviation: symbols & what they represent? 3 categories

A

POP standard deviation: σ
Sample standard dev:
–> SD or S (big “S”)

Est. pop standard dev:
–> s, ŝ (little “s”)

25
Q

Estimated pop SD? Symbol? Why? How to calculate it?

A
  • symbol: ŝ (sometimes little “s”)
  • Sample SD is always too small
  • Affected by sample size
  • N-1 in denominator fixes it
26
Q

Confidence interval / interval estimate def? Descriptive or inferential??

A
  • range of plausible values for pop. parameter centered around the point estimate (usually mean)
  • inferential!! allow you to infer about the population
27
Q

Why is the point est. in the middle of the CI?

(hint: how is it calculated?)

A
  • the CI is constructed by adding and subtracting the margin of error to the point estimate
28
Q

What does a narrow vs wide CI tell us?

A
  • That we are more/less precise or sure of our point estimate
  • Narrower is much better
29
Q

How to tell if population mean estimates are pretty similar or not based on their CI?

A
30
Q

Effect size: what’s it called? what does it measure, what are the units? what if it’s 0?

A
  • Cohen’s d
  • measures the difference between means of 2 groups
  • units: standard deviation units
  • d=0 if means are the SAME
31
Q

What does effect size (d) tell you about the groups?

A
  • the amount of overlap between the distributions
  • how much the change in level of IV actually affected the DV you’re measuring

psych stats (300) (4 decks)

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