Unit 1 - Descriptive Statistics

Question 1

What are the measures of central tendency?

Answer 1

Mean, Median, Mode.

Question 2

How is the mean calculated?

Answer 2

Add all numbers together, divide by number of participants.

Question 3

How is the median calculated?

Answer 3

Middle number, put numbers into order ranging from lowest to highest, choose middle.

Question 4

How is the mode calculated?

Answer 4

Most occurring.

Question 5

What is a strength of the mean?

Answer 5

Accurate average, and takes into account all the scores.

Question 6

What is a weakness of the mean?

Answer 6

Outlier scores can skew the mean to not reflect most participants.

Question 7

What is a strength of the median?

Answer 7

Not affected by outlier scores, so results will not be skewed.

Question 8

What is a weakness of the median?

Answer 8

Does not take into account all scores.

Question 9

What is a strength of the mode?

Answer 9

Can be used for non-numerical data.

Question 10

What is a weakness of the mode?

Answer 10

Impossible to calculate if all data is different, or the may be more than one mode.

Question 11

What are the measures of dispersion?

Answer 11

Range, Variance, Standard Deviation.

Question 12

How is the range calculated?

Answer 12

Largest score minus smallest score.

Question 13

How is the variance calculated?

Answer 13

For each condition, calculate the mean. Within each, subtract each participant’s score from the mean for that condition (‘d’ difference). Then square each ‘d’ score (d^2). Then add all d2 scores together to get Ed2, then subtract by n-1.

Question 14

How is standard deviation calculated?

Answer 14

Square root of variance.

Question 15

What is a strength of range?

Answer 15

Quick and easy to calculate.

Question 16

What is a weakness of range?

Answer 16

Data can be skewed by outliers, only takes into account top and bottom values.

Question 17

What is a strength of variance?

Answer 17

Takes into account all values, less likely to be affected by outliers.

Question 18

What is a weakness of variance?

Answer 18

Only takes into account the squared values, not original units the data was first in.

Question 19

What is a strength of SD?

Answer 19

Takes into account all data, expressed in same unit as original.

Question 20

What is a weakness of SD?

Answer 20

Time consuming and more difficult to calculate than range.

Question 21

How to convert fractions to a percentage?

Answer 21

Divide top of fraction by bottom, multiply by 100.

Question 22

How to convert a percentage to a fraction?

Answer 22

Write percentage over 100, simply fraction, if not a whole number, multiply top and bottom by 10 for every number after the decimal point.

Question 23

How to find actual number of a percentage of an amount?

Answer 23

Divide amount by 100 and multiply by percentage.

Question 24

How to find actual number represented by fraction of an amount?

Answer 24

Divide amount by the denominator (bottom) and multiply by numerator (top)

Question 25

What is a frequency table?

Answer 25

A way of presenting data - tally chart. WHEN = observation | HOW = tally of behaviour

Question 26

What is a line graph and when and how is it used?

Answer 26

Shows behaviour changes over time. Includes X and Y axis, labelled.

Question 27

What, when and how do you use a pie chart?

Answer 27

Works well with nominal data, enables researcher to present percentages, includes labels and titles. WHEN = observation HOW = percentage converted into decimal (divide by 100), 360 multiplied by decimal to calculate the degree.

Question 28

What, when and how do you use a bar chart?

Answer 28

Conveys information about frequencies through height of the bar. WHEN = experiments HOW = (1 mark) data plotted accurately, (1 mark) detailed title, (1 mark) both axis labelled (y axis - mean rating) (x axis - what you’re measuring), (1 mark) mentioning mean rating, y axis must start at 0, bars must be spread apart.

Question 29

What, when and how do you use a histogram?

Answer 29

``` Conveys information about frequencies through area of the bar, used with continuous data, emphasised by the category width. 0< x < 2 (time), frequency (number of people), time (class width), frequency / class width (frequency density). WHEN = experiments HOW = title, axis labelled, bars touching, area represents frequency, unusual class width. ```

Question 30

When and how are scatter graphs used?

Answer 30

``` WHEN = correlations HOW = pattern and strength. ‘uphill’ = positive correlation, ‘downhill’ = negative correlation, ‘spread apart’ = no correlation. ```

Question 31

How are ratios calculated?

Answer 31

= divide the amount of by total number of parts and then multiply by the original ratio.