Trying an ExperimentTrying an Experiment

BATsBATs

Conduct a memory experiment with real Conduct a memory experiment with real participants in a professional and ethical participants in a professional and ethical wayway

Collect dataCollect data

• Have you got all your materials ready?

• We will be testing year 11 students period 1

• After we have collected the data we will analyse it back in HU7 or the Bath Spa room.

Descriptive Statistics Descriptive Statistics

BATsBATs Use measures of central tendency (mode, Use measures of central tendency (mode,

median and mean)median and mean) Analyse the advantages and Analyse the advantages and

disadvantages of each type of descriptive disadvantages of each type of descriptive statistics.statistics.

Draw graphs and interpret data from real Draw graphs and interpret data from real experimentsexperiments

Descriptive StatisticsDescriptive Statistics

Measure of central tendencyMeasure of central tendency Gives a typical value for the data setGives a typical value for the data set Tells you where the middle of the data set isTells you where the middle of the data set is

Measure of dispersionMeasure of dispersion Indicates how the data are spread outIndicates how the data are spread out Tells you what the rest of the data are doingTells you what the rest of the data are doing

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Descriptive StatisticsDescriptive Statistics

The aim of descriptive statistics is to give The aim of descriptive statistics is to give an accurate summary of the dataan accurate summary of the data

The wrong choice of statistic gives a The wrong choice of statistic gives a distorted picture of the datadistorted picture of the data

This can lead to the wrong conclusions This can lead to the wrong conclusions being drawn from the databeing drawn from the data

Each measure of CT and D has its Each measure of CT and D has its advantages and disadvantagesadvantages and disadvantages

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Measures of Central TendencyMeasures of Central Tendency

The meanThe mean AdvAdv: it uses all the values in the set, so is : it uses all the values in the set, so is

most sensitive to variations in the datamost sensitive to variations in the data DisDis: it can be artificially raised or lowered by : it can be artificially raised or lowered by

an extreme value, or by skewed dataan extreme value, or by skewed data

Use it when the data are normally Use it when the data are normally distributed, unskewed and there are no distributed, unskewed and there are no outliersoutliers

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Measures of Central TendencyMeasures of Central Tendency

The medianThe median AdvAdv: it is based on the order of the data, not : it is based on the order of the data, not

their actual values, so not distorted by their actual values, so not distorted by extreme valuesextreme values

DisDis: however, this makes it less sensitive to : however, this makes it less sensitive to variations in the datavariations in the data

Use it when you can’t use the mean Use it when you can’t use the mean because of skew, outliers etc.because of skew, outliers etc.

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Measures of Central TendencyMeasures of Central Tendency

The modeThe mode AdvAdv: it’s the only measure suitable for : it’s the only measure suitable for

summarising category/frequency datasummarising category/frequency data DisDis: for many data sets there is no modal : for many data sets there is no modal

value, or their may be severalvalue, or their may be several

Use when dealing with frequency data, Use when dealing with frequency data, and/or where there is a clear modal value and/or where there is a clear modal value in the setin the set

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Which stats would you choose?Which stats would you choose?

In groups of 3 read the ‘Choice of In groups of 3 read the ‘Choice of Statistics worksheetStatistics worksheet

Discuss q 1 and 2 – which measure of Discuss q 1 and 2 – which measure of central tendency would be best for each central tendency would be best for each list of data?list of data?

1. Should have chosen the colour that was picked most often – the mode

a. Mean, b. mode, c. mean or median ( numbers in order), d. mode, e. Median (mean not best because a few

outliers)

Measures of DispersionMeasures of Dispersion

Range: Simple measure of dispersion- shows the

total spread of data. Difference between highest and lowest

scores in a set of data: top value minus bottom value plus 1.

Affected by atypical, extreme values. Interquartile ranges can also be used

see p 119 Exploring Psychology

Measures of DispersionMeasures of Dispersion

Standard Deviation: Measure of dispersion- shows degree of

clustering of values around the mean. Calculating standard deviation (S): Square

root of sum of all squared deviations from the mean, divided by N (or sometimes N-1).

The smaller the sd the closer the scores are to the mean, high sd = scores spread out a long way from mean.

Measures of DispersionMeasures of Dispersion

Standard Deviation: The most accurate measure of

dispersion – It is more precise than range because all

values are taken into account BUT … have to calculate it – time

consuming

Displaying DataDisplaying Data

TablesTables – clear headings with units of – clear headings with units of measurement measurement

GraphsGraphs – – see findings at a glancesee findings at a glance Bar chart – discrete categories, bars separatedBar chart – discrete categories, bars separated HistogramHistogram – x axis has continuous data, no – x axis has continuous data, no

gaps between bars (DV on x axis, frequency on gaps between bars (DV on x axis, frequency on y axis)y axis)

Line graph/frequency distribution curveLine graph/frequency distribution curve e.g e.g Yerkes- Dodson curveYerkes- Dodson curve

What type of graph?What type of graph?

What types of graph are used in each of the What types of graph are used in each of the following…following…

Murdock (1962) p16Murdock (1962) p16

Van Ijzendoorn and Kroonenburg (88) Van Ijzendoorn and Kroonenburg (88) p57/8p57/8

Frequency distribution curve

Bar chart

PlenaryPlenary

Answer the questions 1, 4,5,6 and 7Answer the questions 1, 4,5,6 and 7

Use the answer sheet to mark your Use the answer sheet to mark your answersanswers

Using your own dataUsing your own data

BATBAT

Draw graphs and interpret data from your Draw graphs and interpret data from your own experimentown experiment

Evaluate the work of othersEvaluate the work of others

Over to youOver to you

Select the most appropriate descriptive Select the most appropriate descriptive stats for your data (central tendency and stats for your data (central tendency and dispersion) and calculatedispersion) and calculate

Display your data in a graph of your Display your data in a graph of your choicechoice

What does your data tell you? What does your data tell you? Will you accept or reject your hypothesis?Will you accept or reject your hypothesis? How could you improve your method?How could you improve your method?

Peer ReviewPeer Review

Before a piece of Psychological research Before a piece of Psychological research can be accepted it is reviewed by other can be accepted it is reviewed by other psychologists to check the work’s validity psychologists to check the work’s validity and reliability.and reliability.

Read the method, and data analysis of Read the method, and data analysis of someone in a different group.someone in a different group.

Would you accept their work?Would you accept their work? How could reliability and/or validity be How could reliability and/or validity be

improvedimproved

Plenary and HomeworkPlenary and Homework

HomeworkHomework – complete the worksheet by – complete the worksheet by next lessonnext lesson

Start to Revise for Mock exam – use the Start to Revise for Mock exam – use the blog quiz!! The results will be emailed to blog quiz!! The results will be emailed to meme