Research methods: descriptive statistics

State measures of central tendency

- mean

- mode

- median

State advantages of mean

- uses all the data so is most powerful

State disadvantages of using mean

- doesn't like outlying values

State advantages of median

- not affected by outliers

State disadvantages of median

- doesn't like small groups of data

State advantages of mode

- that figure actually does occur in that sequence

State disadvantages of mode

- tells us nothing about the other values

State measures of dispersion

- range

- standard deviation

What is the range

- difference between the highest and lowest score

What is the standard deviation

- from the mean: tells you how spread out the values in a distribution are from its mean

- it plots your score and compares it with the population/normal distribution - it tells you where you are compared to others

- it measures how much, on average, scores differ from the mean (high SD = spread out, low = close together)

State advantages of range

- easy to calculate

Disadvantages of range

- distorted by anomolies

Advantages standard deviation

- not skewed by anomalies

- representative of all data

Disadvantages of standard deviation

- difficult to calculate

Describe bar charts - what is on x-axis&y-axis

- show data in the form of categories to be compared

- categories are on the X axis

- what you are measuring on the y-axis

- bars should be the same width but not touch

What type of data should be presented in a bar chart

- words and numbers

What is on each axis on histograms

- how often something happened (y-axis_ in each category (x axis)

- dependant variable is along the bottom

What type of data is presented in a histogram

- continuous data

Difference between histogram and bar charts

- bar chart: bars have to be the same width but NOT touch

- histograms: bars can be different widths and can touch

What is a skewed distribution?

- if a distribution of scores is not symmetrical it will be skewed (no even distribution of score either side of the mean)

What causes skewed distribution

- outliers

What is a positive skewed distribution

- occurs when there is a high extreme score

- so it contains more low than high scores

What is negative skewed distribution

- occurs when there is a low extreme score

- so it contains more high than low scores