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Research > Lecture 4 > Flashcards

Lecture 4 Flashcards

1
Q

What are descriptive statistics?

A

Methods for organizing and summarizing data

example: table or graph

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2
Q

A descriptive value for a population is called a __________

A

parameter

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3
Q

a descriptive value for a sample is called a ___________

A

statistic

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4
Q

What does the Mu symbol represent?

A

The mean for a population

NOT a sample

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5
Q

Frequency Distribution vs Grouped Frequency Distribution

A

Frequency distribution- presents organized picture of entire set of scores

Grouped frequency distribution- Some statistics are grouped together to accomadate for a wider range of scores

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6
Q

If the scores in a population are measured on an interval/ratio scale and the N is large…. the data will present as a ___________

A

smooth curve instead of a jagged histogram

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7
Q

T or F: a smooth curve shows the exact frequency of every score

A

F

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8
Q

Describe a normal distribution

A

symmetrical bell shape

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9
Q

What is a skew of frequency distribution?

A

Nonsymmetrical distribution of data

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10
Q

What kind of skew is this?

A

Positive skew

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11
Q

What kind of skew is this?

A

Negative skew

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12
Q

What is Kurtosis of a graph?

A

The “peakedness” of the distribution

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13
Q

Leptokurtic vs Platykurtic

A

Describe the Kurtosis of a graph

Leptokurtic = High, thin peak

Platykurtic = lower/broader peak

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14
Q

How does a stem and leaf distribution work?

A

Each score divided into stem and leaf

the stem contains the first digit(s) and the leaf contains the final digits

example: 3//3582 represents the scores 33 35 38 32

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15
Q

What are 3 measures of central tendency?

A

Mode Median and Mean

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16
Q

Bimodal vs Multimodal

A

Having 2 modes vs having multiple modes

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17
Q

Mode definition

A

Most frequently occuring number

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18
Q

What kind of data is appropriate for using a Mode?

A

All types: Nominal, Ordinal, Interval, and Ratio

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19
Q

Median definition

A

If the scores are listed smallest to largest, it is the midpoint of the list

If odd numbers, it’s the middle number

if even numbers, its the average of the middle 2 numbers.

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20
Q

What kind of data is appropriate for use of the median

A

Ordinal Interval and Ratio data

NOT nominal

21
Q

What is one advantage of using the Median?

A

It is relatively unaffected by extreme scores

22
Q

The Mean can be used as a representation of central tendency for what kind of data?

A

Interval and Ratio

NOT Nominal or Ordinal

23
Q

When should we not report the mean?

A

When there are extreme scores that will pull the mean in one direction

When you’re using a nominal scale

24
Q

In a central distrubtion, the mean and median will ____________

A

Always be equal and always be in the middle

25
Q

(mean, median, mode)

In a skew, what stays in the middle of the curve?

What is skewed most towards the tail?

What is in the middle?

A

Mode

Mean

Median

26
Q

Descriptive statistic vs inferential statistic in variability:

A

A descriptive statistic measures the degree to which scores are spread out

Inferential statistic measures how accurately an individual score or sample represents an entire population

27
Q

A _______ variability means scores will more liekly give a good view of the whole population

A

Low

28
Q

How to measure range for this set?

4, 5, 7, 8, 9, 11

A

11- 4 = 7

29
Q

How to calculate standard deviation for a sample?

A
  1. First calculate the variance of every score from the mean. Each score - the mean
  2. Square all of those numbers and add them together
  3. Divide by N - 1 if it’s for a sample, just N if it’s for a population
  4. Take the square root of the answer
30
Q

what does n-1 represent when calculating standard deviaton?

A

Degrees of freedom

31
Q

On a normal distribution __% of scores will be 1 standard deviation from the mean

A

70%

32
Q

On a normal distribution __% of scores will be 2 standard deviations from the mean

A

95

33
Q

On a normal distribution __% of scores will be 3 standard deviations from the mean

A

99

34
Q

What does a Z score tell you?

A

Gives you context of how a score relates to other scores in the distribution

35
Q

How to calculate a Z score?

A

(Score - Mean) / Standard Deviation = Z score

note: Z score will always be a really small number

36
Q

What are inferential statistics?

A

Methods for using sample data to make general conclusions about a population using probability

Rather than just describing the data like descriptive statistics

37
Q

When graphed on a normal distribution, probability can be defined as the ____________________ the curve

A

the portion under the curve

38
Q

Are Z scores for populations or samples?

A

Populations, not samples

39
Q

How to use a Z score table?

A

You can use a coresponding Z score to find the probability that something will fall into the body vs the tail of the graph

40
Q

Z scores will only work if the data has a _______ distribution

A

normal

41
Q

If you sample _____ people you will end up with a normal distribution

A

30

42
Q

What is the central limit theorem?

A

As sample size increase it approaches a normal distribution

30 will have a more normal distribution than 15

43
Q

T or F: population data can be any size or any shape, but if you have a sample of 30+ it will be very close to normal distribution

A

T

44
Q

What is SEM (Standard Error of the Mean)

A

Difference between Sample Mean and True Population mean

45
Q

What is the difference between SEM and SD?

A

Standard Deviation compares the amount of variability of a set of data, from the mean

SEM- measures how far the sample mean is likely to be from the population mean

SEM is ALWAYS smaller than SD

46
Q

How do you calculate SEM?

SD of sample: 5

Sample size: 50

A

50/ SqRt(5)

The smaller the number = less sampling error likely

47
Q

What is a point estimate vs an interval estimate?

A

These are ways to use estimates to represent a population

Point estimate- using the mean of your sample

Interval estimate- using a span of numbers that includes the mean

48
Q

What is a confidence interval/interval estimate

A

Range of numbers inferred from the sample that has a known probability of capturing the true population parameter

Example: AVG GPA = 3.4 with a 95% confidence interval that it’s between 3.2 and 3.6

Research (12 decks)

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