Module 14: Descriptive statistics

Question 1

2 most common ways to sumamrize data

Answer 1

1. measure of central tendency
2. Measure of variability

Question 1

Measure of central tendency (4)

what it is + represented by

Answer 1

A measure of the typical value in a collection of numbers or a data set
- measured by mean, median and mode

Question 2

Mean (2)

+ how to find?

Answer 2

The average
Sum of all the scores divided by the total number of scores

Question 3

Population mean

Answer 3

Question 4

Sample mean

Answer 4

Question 5

Median (2)

How to find?

Answer 5

The value that lies in the middle of the data when the data set is ordered
- First rank the data, then the position of the median is equal to the number of enteries plus one divided by 2

Question 6

Odd number of entries when caculating median:

Answer 6

median is the middle data entry

Question 7

Even number of entries when calculating median:

Answer 7

Median is the mean of the 2 middle data entries

Question 8

Mode

Answer 8

The most frequent value

Question 9

If no data set is repeated then the data has no

Answer 9

mode

Question 10

If two entries occur with the same greatest frequency each entry is a — and is called

Answer 10

• mode
• bimodal

Question 11

Finding the mode

Answer 11

finding the greatest frequency

Question 12

Advantage of using the mean (2)

Answer 12

• most common statistic
• Takes into account every entry of a data set

Question 13

Disadvantage of using the mean (2)

Answer 13

• greatly affgected by extreme scores (outliers)
• Knowledge about individual cases is lost with averages

Question 14

Advantages of using the median (2)

Answer 14

• Little influence by extreme scores
• Reasonable estimate of what most people mean by the center of a distribution

Question 15

Disadvantage of using the median

Answer 15

• may not be good to ignore extreme values

Question 16

Advanatges of using the mode (2)

Answer 16

• the most frequently obtained score
• not influenced by extreme score

Question 17

Disadvanatge of using the mode (2)

Answer 17

• may not represent a large proportion of the scores
• ignores extreme values

Question 18

Variability

Answer 18

numbers which describe how spread out a set of data is

Question 19

Examples of variability meausres (4)

Answer 19

• range (interquartile range)
• deviation
• variance
• standard deviation

Question 20

Range+ formula (2)

Answer 20

length of the smallest interval that contains all the data

range= largest value - smallest value

Question 21

range is sensitive to

Answer 21

• sample size: small samples= less range (less respresentative range)
• extreme scores (tells you smallest and largest but not bulk)

Question 22

Interquartile range (2)

+ formula

Answer 22

Measure of distance between first and third quartiles
- IQR= Q3-Q1

Question 23

second quartile is the

Answer 23

median

Question 24

benefits of IQR (2)

Answer 24

- less affected by extreme values - helpful for identifying outliers

Question 25

Quartile (2) | What it is+median

Answer 25

- positions in a range of values representing multiples of 25% - 50% of scores fall below median, 50% scores above

Question 26

First quartile (Q1)

Answer 26

25% of scores fall below Q1, 75% above

Question 27

Third quartile (Q3)

Answer 27

75% of scores fall below Q3, 25% above

Question 28

deviation

Answer 28

The diference between each score and the mean of the data set | How far you are from the mean

Question 29

deviation formula

Answer 29

xi= xi-u

Question 30

deviation scores always sum to

Answer 30

0

Question 31

Difference between deviation and IQR/boxplots

Answer 31

Deviation scores show dispersion around the mean, IQR and boxplot show dispersion around the median

Question 32

Variance

Answer 32

single number representing the average amount of variation in a set of scores/ how spread out the scores are

Question 33

Steps for finding the sample variance (5)

Answer 33

Question 34

Standard variation

Answer 34

Measure of the spread of scores out from the mean of the sample

Question 35

How to cauclate standard deviation

Answer 35

1. calculate the variance 2. find the square root

Question 36

Population standard deviation formula

Answer 36

Question 37

Standard deviation is a measure of the typical amount an entry deviates from the mean, thus the more entries are spread out, the

Answer 37

greater the standard deviation

Question 38

Descriptive statistics (2)

Answer 38

- cannot make predictions or generalizations - only drawing conclusions about current sample and not extrapolating or going beyond

Question 39

inferential statistics (2)

Answer 39

- can make predictions or generalizations - allow conclusions about the population based on data from a sample

Question 40

Data matrices

Answer 40

a table or worksheet that organizes the data together with all the variables of interest

Question 41

Frequency distributions

Answer 41

A table indicating the frequency of each value in a data set

Question 42

Histogram (3) | What it is+ illustrates+can help identify

Answer 42

- A graphical representation of the frequency of a variable - illustrates the distribution of scores - can help identify outliers or violations of normal distribution assumptions

Question 43

Answer 43

symmetrical

Question 44

Answer 44

Negative skew or left skew

Question 45

Answer 45

Positive skew/right skew

Question 46

Central tendency

Answer 46

helps identify the typical or most common value in data

Question 47

Measures of central tendency

Answer 47

Mean median mode

Question 48

measure of central tendency for symmetrical distribution/ skewed

Answer 48

Question 49

If the average is 100 and the standard deviation is 10, then there is

Answer 49

2/3 of the data that falls between 90 and 110

Question 50

for data that is skewed or has outliers, ---- may be better choice to describe the centre of the distribution

Answer 50

median

Question 51

Q position

Answer 51

Qposition= [(Q#)(n+1)]/4 | Q#= number of quartile your trying to find

Question 52

Round Q position to

Answer 52

the median

Question 53

How to find outlieers with IQR

Answer 53

Question 54

Scatterplots

Answer 54

- visualize the form, direction and strength of 2 variable relationships

Question 55

correlation coefficients

Answer 55

indicate the degree of covariance between variables: how much one variable changes in relation to another

Question 56

Data points that are more closely positioned around the best fit line represent

Answer 56

a stronger relationship than when data points are further from the lines