Descriptive Statistics

Question 1

Point statistics

Answer 1

Single values, or points that summarise a set of data such as mean or median

Question 2

Interval estimates

Answer 2

Tend to be a range of values that summarise set of data such as variance or standard deviation

Question 3

Visualisations

Answer 3

Figures that help display the point and interval estimates of data and can take various forms depending on data type

Question 4

The mean

Answer 4

Measures average of a set of numbers

Question 5

25 participants are asked how many years they have been driving. They response 7,1,2,6,3,4,3,4,3,4,5,4,7,5,6,5,5,4,5,6,5,6,3,2,5. Calculate the mean?

Answer 5

7,1,2,6,3,4,3,4,3,4,5,4,7,5,6,5,5,4,5,6,5,6,3,2,5 = 110
110/25(amount of numbers) = 4.4
X = 4.4 or M = 4.4

Question 6

The median

Answer 6

Point estimate that is the middle number of a distribution where half are large and half are smaller. Divides the data in half

Question 7

How to calculate the median

Answer 7

Sort values highest to lowest (sort from i(first value) to n(last value))
median is value at position (n + 1)/2
Count how many are in the row and divide by 2

Question 8

What is the median position of 7,1,2,6,3,4,3,4,3,4,5,4,7,5,6,5,5,4,5,6,5,6,3,2,5

Answer 8

1,2,2,3,3,3,3,4,4,4,4,4,5,5,5,5,5,5,5,6,6,6,6,7,7 =25
Median position = (n+1)/2 = (25+1)/2 =26/2
Median position = 13
Position 13 = 5 median =5

Question 9

What is the median of 20,20,10,12,10,14,12,20,14,14,14,13

Answer 9

10,10,12,12,13,14,14,14,14,20,20,20
Median position = (n+1)/2 = 12+1/2 = 6.5
Median = 14

Question 10

The mode

Answer 10

Last point estimate, the value of category that appears most often in data set

Question 11

How to calculate mode

Answer 11

Sort data set from smallest to largest
What number is there most frequently = mode

Question 12

Calculate mode of 3,4,6,4,6,6,2,2,3,6,6

Answer 12

2,2,3,3,4,4,6,6,6,6,6
Mode = 6

Question 13

Inferential

Answer 13

Statistic that allow you to make predictions about or comparisons between data (e.g., t-value, F-value, rho)

Question 14

Z-scores

Answer 14

Any value on a continuous scale can be converted to a z-score (standard deviation units)

Question 15

Confidence intervals

Answer 15

Specifically focus on 95% confidence interval using cut of value (assuming a =.05 and two-tailed) of z = 1.96 using key formulas:

Upper 95% CI = x + (z x SE)
Lower 95% CI = x - (z xSE)

Question 16

One sample t-test

Answer 16

Compare your sample mean to a known test value. For example, compare sample IQ to population norm of 100

Question 17

Between subjects t-test

Answer 17

Compare two groups or conditions where the participants are different in each group and have not been matched on broad demographics e.g only age

Question 18

Within subject t-test

Answer 18

Compare two conditions where the participants are the same in both conditions matched on demographics such as IQ, reading ability but must be marched on certain number

Question 19

Pearson correlation

Answer 19

Pearson product moment correlation measures the relationship between two variables that is the monotonic and linear. Measures the covariance or shared variance that standardises measure between -1 (the perfect negative relationship) and 1 (perfect positive relationship)