1. 1.3 Data Recording, Analysis and Presentation
Design of raw data recording tables
Use of raw data recording tables
Standard and decimal form
Significant figures
Estimations from data collected

2. This is raw data >>>
Psychological investigations that collect quantitative data tend to generate quite a lot of results – one or more scores for each ppt
This is raw data >>>
Unprocessed
In purest form

3. Psychologists may wish to present raw data in a number of ways:
Fractions
Decimal form
Standard form
Percentage
Ratio
Significant figures

4. Fractions

5. Decimal form

6. Standard form

7. Percentage

8. Ratio

9. Significant figures

10. In psychology, we take the raw data found and can run…
Descriptive statistics
Inferential statistics

11. 1. Descriptive statistics
Descriptive statistics are broken down into two categories:
Measures of central tendency
Measures of dispersion

12. Measures of central tendency
There are different measures of central tendency:
The mean
The mode
The median

13. The mode The mode is the most frequent score in a set of results
EXAMPLE:
Note; you should always write the numbers in order to see the most frequent number with ease

14. The mode
If two or more scores are equally common there will be two or more modes
EXAMPLE

15. THE MODE
A researched asks participants to decide whether their last dream was active, inactive, or mixed. The researcher found out of 50 people 12 said active, 36 said inactive, and 2 said mixed. The mode would be 36/50 inactive

16. The mode Summary: MOST COMMON Effective when data is nominal
Categorises only – does not describe accurately when there are more than one mode
Very unrepresentative of data

17. Both medians are similar
The median
To calculate the median you need to present the data in order from smallest to largest. You then select data in the middle of the list Scores with an even number of data? There will be two middle numbers. These should be added together and divided by two Example Bus drivers: =42 42/2=21 so the median is 21 Non bus drivers: =44. 44/2=22. so the median is 22
Both medians are similar
This suggest there is nondifference between intelligence of bus drivers and non bus drivers

18. The median Summary: MIDDLE MOST NUMBER Not affected by extreme scores
Value may not actually appear in data set
More tedious than mode and mean

19. The mean Usually called the 'average’
The mean is calculated by adding up all the scores in the data set by dividing the total number of scores. This does include any 0’s

20. The mean Summary: THE AVERAGE
 Makes use of all the values in the data set
 If extreme values are included it can distort results

21. What types of data can be used?
The mode can be used with any type of data. It is the only measure of central tendency that can be used with nominal data
The median cannot be used with nominal data, but can be with any other type of data
The mean can only use interval or ratio data

22. Graphs and tables A3 handout
LINE GRAPH
BAR GRAPH
PIE CHART
SCATTER DIAGRAM
HISTOGRAM

23. What is your favourite Psychologist?
Freud?
Milgram?
Bandura?
Sperry?
Loftus?
Tally up the number of responses for each psychologist

24. You should now convert these numbers into decimals You should divide the value by the total number of values Example: Freud… 8 people out of 20 8/20 =0.4

25. Now convert these into percentages
Times the decimal by 100 EXAMPLE: Freud 8 people out of 20 8/20 = x 100 = 40%

26. Let’s create a pie chart
To draw a pie chart you will need a protractor.
Firstly draw a circle, then each portion of the pie can be worked by the percentage of the 360 degrees of a circle.
This done by multiplying the decimal x 360
Freud
8 people out of 20
8/20 = 0.4
0.4 x 360 = 144

28. The second component of descriptive statistics is…
MEASURES OF DISPERSION
Range
Variance
Standard deviation

29. The range Identify the largest and smallest value
Remember with this example the medians were similar
In this case, the ranges are quite different
This tells us about the diversity of ability amongst bus drivers
Identify the largest and smallest value
Subtract the smallest value from the largest value
Then add 1
Example
Bus drivers:
30 – 11 = 19, 19+1 = 20… Range = 20
Non bus drivers:
39 – 1 = 38, 38+1 = 39…. Range = 39

30. The range
Not representative of data set when there is extreme scores – one really large number or really small number (ie an outlier)
Fails to take into account quantity of numbers involved

31. The variance
Just as the mean can tell us more than the mode, the measurement ‘variance’ tells us more than the range
Rather than looking only at extreme scores of the data set, the variance considers the difference between each data point and the mean – this is called the deviation

32. The variance These deviations are then squared Added together
Then the total is divided by the number of scores in the data set
And then minus one
This is represented by the formula

33. Variance Before we begin to calculate, note you always do the
parts of the sum in brackets first
EXAMPLE DATA SET
BUS DRIVERS: 2, 15, 6, 8, 14, 19, 9, 4, 8, 13

34. Variance Step 1: calculate the mean (x̄)
Add all the numbers together: 98
Divide the total by the total number in data set: 10
98+10 = 9.8
Therefore, mean (x̄) = 9.8

35. Variance
Step 2: Write down the number of scores (n) In this case n=10

36. X
X - (x̄)
(X-x̄)² 2 15 6 8 14 19 9 4 13
Variance
Step 3: Draw a table with 3 column and write the scores (values of X) down in the first column

37. X
X - (x̄)
(X-x̄)² 2
7.8 15
5.2 6
3.8 8
1.8 14
4.2 19
9.2 9
0.8 4
5.8 13
3.2
Variance
Step 4: Work out the difference between each score Remember: X-x̄ = =5.2

38. Variance Step 5 Square each of these differences X X - (x̄) (X-x̄)² 2
7.8
60.84 15
5.2
27.04 6
3.8
14.44 8
1.8
3.24 14
4.2
17.64 19
9.2
84.64 9
0.8
0.64 4
5.8
33.64 13
3.2
10.24
Variance
Step 5 Square each of these differences

39. Variance Step 6 Add together the column of differences X X - (x̄)2
7.8
60.84 15
5.2
27.04 6
3.8
14.44 8
1.8
3.24 14
4.2
17.64 19
9.2
84.64 9
0.8
0.64 4
5.8
33.64 13
3.2
10.24
225.6
Variance
Step 6 Add together the column of differences

40. Variance
Step 7 Take the total (255.6) and divide this by n-1 (10-1) = 28.4

41. Variance
The variance tells us about the dispersion of a group (how varied the results are)

42. Standard deviation
If the mean is 3.08 and the SD is 0.64 This means the data on average is 0.64 above (3.72) or below (2.44) the mean

43. Standard deviation
The variance is always written squared. If you find the square root of 28.4 = 5.33 (SD) . Each data point is on average 5.33 away from the mean (9.8) SD = 5.33