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Stats Midterm > Lecture 3 > Flashcards

Lecture 3 Flashcards

1
Q

What are the 2 major classes of statistics?

A

Descriptive

Inferential

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2
Q

What type of statistics summarize aspects of samples or populations?

A

Descriptive statistics

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3
Q

What are all members of a group that share a common characteristic of interest?

A

Population

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4
Q

What is a subset of a population that shares the same characteristic of interest?

A

Sample

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5
Q

We do research with samples because we don’t have access to what?

A

Entire populations

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6
Q

What are used to make generalizations (inferences) from samples to populations?

A

Inferential Statistics

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7
Q

Choosing a good sample affects what?

A

External validity

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8
Q

What is the ability to generalize findings outside the sample?

A

External validity

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9
Q

What type of sample adequately represents the population of interest?

A

Representative sample

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10
Q

What type of sample does not adequately reflect the population?

A

Biased Sample

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11
Q

What are the 2 major sampling strategies?

A

Probability

Non-probability

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12
Q

Probability sampling uses what to choose a sample representative of the population to avoid bias?

A

Random selection

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13
Q

Non-probability sampling doesn’t use random sampling so there is no guarantee of what?

A

that is represents a larger population

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14
Q

What are the probability sampling methods?

A

True random sampling
Stratified random sampling
Systematic random sampling
Multi-stage random sampling

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15
Q

In true random sampling every person in the population has?

A

An equal

Independent chance of being selected

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16
Q

In stratified random sampling we identify subgroups in the population and randomly sample from these groups to get what?

A

Same proportions in sample as represented in population

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17
Q

What type of sampling randomly selects a starting place to choose participants?

A

Systematic random sampling

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18
Q

What is used in systematic random sampling?

A

Systematic rule to select particiapnts

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19
Q

In multi-stage random sampling the final random sample is selected through what?

A

Series of random selection decisions used to eliminate potential particiapnts

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20
Q

What are the non-probability sampling methods?

A 
Convenience 
Purposive
Quota
Systematic (non-random)
Stratified (non-random)
Multi-stage (non-random)
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21
Q

In convenience sampling the sample is choosen based on what?

A

Convenient access

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22
Q

In purposive sampling the sample is formed by including what?

A

Available persons who meet a specific criterion, but not randomly.

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23
Q

In quota sampling individuals of a specified group are added to the sample until when?

A

Until a pre-specified number is met but not randomly

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24
Q

In systematic (non random) sampling the same is selected how?

A

Through a systematic, not random process

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25
Q

With stratified (non random) sampling the sample is selected how?

A

To have a specified ratio for each target group but not randomly

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26
Q

In multi-stage (non-random) sampling, the final sample is selected how?

A

Through a series of non random selection decisions used to eliminate groups of potential particiapnts

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27
Q

What type of sampling is it when stratified samples are selected from designated age groups at the same point in time so the effect of age can be examined?

A

Cross-sectional sampling

28
Q

What type of sampling is it when a single sample of participants is measured repeatedly over time so the effect of age or time can be examined?

A

Longitudinal Sampling

29
Q

What type of sampling is it when repeated samples of the same population are measured over time so the effect of time can be examined?

A

Trend Sampling

30
Q

What type of sampling is a subset of the population that is repeatedly sampled over times so the effect of time can be examined among the subset?

A

Cohort sampling

31
Q

What is a count of the number of times a value occurs?

A

Frequency

32
Q

What is the term for a distribution showing the frequency for each value of the variable

A

Frequency distribution

33
Q

Frequency distributions usually include what other statistics?

A

Percent
Valid percent
cumulative percent

34
Q

What are the shapes of distributions?

A

Skew

Kurtosis

35
Q

What are the types of skew?

A

Symmetrical
Negative
Positive

36
Q

A symmetrical skew means what?

A

Normal (mean,median,mode are the same)

37
Q

A negative skew means what?

A

Mean is lower than median

38
Q

A positive skew means what?

A

mean is higher than median

39
Q

What does the skew tell you?

A

How much the distribution deviates from symmetry

40
Q

What is kurtosis?

A

Peakedness or flatness of distribution

41
Q

What is a skewness of 0?

A

Perfectly symmetrical distribution (normal)

42
Q

What is a skewness < (less than)2 (not 0)?

A

Normal enough

43
Q

What is a skewness > (greater than)2 (not 0)?

A

Skewed

  • positive = positive skew
  • negative = negative skew
44
Q

What is the typical or most commonly occurring observation in the data?

A

Central Tendency

45
Q

Central tendency includes?

A

Mode
Median
Mean

46
Q

What is the most frequently occurring score in distribution?

A

Mode

47
Q

What is the score that divides the distribution in half in the middle?

A

Median

48
Q

What is the average?

A

Mean

49
Q

The mean gives the most what?

A

Information from data

50
Q

What allows you to determine how much the scores are clustered around the center of a distribution or how far out they are dispersed (spread)?

A

Measures of dispersion

51
Q

What are the 4 main measures of dispersion?

A

Range
Semi-interquartile Range
Standard Deviation
Variance

52
Q

What is a very crude measure of dispersion?

A

Range (highest score-lowest score)

53
Q

What is a better but not to meaningful measure of dispersion?

A

Semi-interquartile range

54
Q

What is the percentage of score that fall below a value?

A

Percentile rank

55
Q

What is the average of the score from the mean?

A

Standard Deviation

56
Q

Standard deviation is used with the mean for?

A

Interval or ratio data

57
Q

What is the average squared deviation of each score from the mean of the distribution

A

Variance

58
Q

What do bodies in box plots display?

A

Location of quartiles

59
Q

What does the lines extending out from boxes display?

A

Distance to the furtherest observations that aren’t outliers

60
Q

What are displayed in box plots as points beyond the lines?

A

Outliers

61
Q

What do z-scores allow us to understand?

A

Individual scores in a distribution

62
Q

What type of variable can be converted into a z score?

A

Any continuous variable

63
Q

What is a standard normal distribution?

A
  • bell-shaped and symmetrical
  • mean, median, mode are equal
  • total area under curve is 1.00
64
Q

What do standardized score represent?

A

How far a score is from the mean in standard deviation units

65
Q

The sign of the z score tells you what?

A 
positive = above mean
negative = below mean
0 = equal to mean

Stats Midterm (6 decks)

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