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psychology inferentail stats in research methods

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  • Created by: Shaheen
  • Created on: 20-03-11 17:32

Inferential Statistics...

Probability: The probability of the results of a study happening by chance and a one off. Its measured using the P Value. The smaller the P value the more reliable the results. A P value of P less than 0.05 is the normal value psychologists use, this means there is 5% chance of it being chance.

Significant: If your test is significant then you can reject your null hypothesis.

Levels of Measurement:

Nominal: The data is put into catergories for example sorting people by height, tall, medium, short...

Ordinal: Data is ordered in some way e.g alphabetically...

Interval: Data is measured in units of equal interval such as counting correct answers...

Type 1 Error: Rejecting the null hypothesis when you shouldn't,P value is too high...

Type 2 Error: Accepting the null hypothesis when you shouldn't, P value is too low...

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Inferential Statistics...

Spearmans Rho...

The Hypothesis predicts a correlation between two sets of data...

Experimental Design: Matched Pairs...

Levels of measurement: Ordinal/Interval...

Step1: State the hypothesis and null hypothesis...

Step2: Record the data and work out the difference...

Step3: Find the observed value of Rho...

Step4: Find the critical value of Rho...

Step5: State the conclusion...

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Chi-Square ...

The Hypothesis predicts a difference between two correlations...

Experimental Design: Independent Measures...

Levels of measurement: Nominal...

Use a contingency table to plot data...

Calculate the DF. DF = (Rows - 1) times (Columns - 1)

Work out the critical value....

If the Observed Value is less than the Critical value then accept the null hypothesis...


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Mann-Whitney U...

The Hypothesis predicts a difference between two sets of data...

Experimental Design: Independent Measures...

Levels of measurement: Ordinal/Interval...

Step1: State the hypothesis and null hypothesis...

Step2: Record the data and allocate points...

Step3: Find the Observed value...

Step4: Find the Critical Value...

Step5: State the conclusion...

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Wilcoxon T...

The Hypothesis predicts a dfference between two sets of data...

Experimental Design: Matched Pairs/Repeated Measures...

Level of measurement: Ordinal/Interval...

Step1: State the hypothesis and null hypothesis...

Step2: Record the data and calculate the difference between scores and rank...

Step3: Find the Observed value...

Step4: Find the Critical Value...

Step5: State the conclusion...

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Measures of central tendency Dispersion...

Measures of central tendency: These try and calculate the average, it used on of these three methods...

The Mean: Add up all of the scores and divide by the number of scores. Its not good for nominal data...

The Median: Its the middle value in an ordered list. Its not appropriate for nominal data...

The Mode: Its the value which is most common in the data. It is appropriate for nominal data, or data in categories...

Measures of dispersion: Trys to tell us about the spread of the data...

The Range: Calculated by finding the difference between the highest and lowest score but might be effected by extreme values...

Standard Deviation: Expresses the spread of data around the mean, all bits of data are examined...

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Justifying choice of inferential test...

Spearman's Rho: A test of correlation is needed as the hypothesis predicted a correlation and the data collected is ordinal...

Chi-Square: As the data has been put into categories and is nominal data, the experiment design was also independent groups...

Mann-Whitney: A test of difference is needed between two groups. Uses independent groups and uses ordinal data...

Wilcoxon: A difference is predicted between two conditions. It will use repeated measures and interval data...

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