Trying an Experiment BATs Conduct a memory experiment with real participants in a professional and ethical way Collect 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 BATs  Use measures of central tendency (mode, median and mean)  Analyse the advantages and disadvantages of each type of descriptive statistics.  Draw graphs and interpret data from real experiments

Descriptive Statistics  Measure of central tendency  Gives a typical value for the data set  Tells you where the middle of the data set is  Measure of dispersion  Indicates how the data are spread out  Tells you what the rest of the data are doing

Descriptive Statistics  The aim of descriptive statistics is to give an accurate summary of the data  The wrong choice of statistic gives a distorted picture of the data  This can lead to the wrong conclusions being drawn from the data  Each measure of CT and D has its advantages and disadvantages

Measures of Central Tendency  The mean  Adv: it uses all the values in the set, so is most sensitive to variations in the data  Dis: it can be artificially raised or lowered by an extreme value, or by skewed data  Use it when the data are normally distributed, unskewed and there are no outliers

Measures of Central Tendency  The median  Adv: it is based on the order of the data, not their actual values, so not distorted by extreme values  Dis: however, this makes it less sensitive to variations in the data  Use it when you can’t use the mean because of skew, outliers etc.

Measures of Central Tendency  The mode  Adv: it’s the only measure suitable for summarising category/frequency data  Dis: for many data sets there is no modal value, or their may be several  Use when dealing with frequency data, and/or where there is a clear modal value in the set

Which stats would you choose?  In groups of 3 read the ‘Choice of Statistics worksheet  Discuss q 1 and 2 – which measure of central tendency would be best for each 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 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 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 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 Data  Tables – clear headings with units of measurement  Graphs – see findings at a glance  Bar chart – discrete categories, bars separated  Histogram – x axis has continuous data, no gaps between bars (DV on x axis, frequency on y axis)  Line graph/frequency distribution curve e.g Yerkes- Dodson curve

What type of graph? What types of graph are used in each of the following…  Murdock (1962) p16  Van Ijzendoorn and Kroonenburg (88) p57/8 Frequency distribution curve Bar chart

Plenary  Answer the questions 1, 4,5,6 and 7  Use the answer sheet to mark your answers

Using your own data BAT Draw graphs and interpret data from your own experiment Evaluate the work of others

Over to you  Select the most appropriate descriptive stats for your data (central tendency and dispersion) and calculate  Display your data in a graph of your choice  What does your data tell you?  Will you accept or reject your hypothesis?  How could you improve your method?

Peer Review  Before a piece of Psychological research can be accepted it is reviewed by other psychologists to check the work’s validity and reliability.  Read the method, and data analysis of someone in a different group.  Would you accept their work?  How could reliability and/or validity be improved

Plenary and Homework  Homework – complete the worksheet by next lesson  Start to Revise for Mock exam – use the blog quiz!! The results will be ed to me