Measures of central tendency Mean Median Mode How is it calculated? ‘ Average’ – Calculated by adding up all the scores and then dividing by the number of scores ‘ Middle score’- calculated by putting all scores in order then picking the middle score The most frequently occurring score

I can explain the difference between a Frequency Diagram, Bar chart, Histogram and Scatter graph I can understand when each one should be used

When do we use them… match them up! Frequency Diagram Bar chart Histogram Scatter graph Used to show a relationship or correlation between two variables Used to show continuous data such as time or number of words recalled Measuring how often something happens Used to show the average or percentages in a data set

I can explain what significance levels are I can explain what type 1 and type 2 errors are

Exam Qs or page 562

Write an directional, non-directional and null hypothesis for this experiment To investigate if boys or girls do better in English GCSE

We found some results!! Measuring A* to C Grades as a pass: We found... Girls 88% Boys 84%

But is the difference Significant… How sure are we that the differences in our results are due to our IV? Or Just due to CHANCE? ◦Were they just lucky with the questions…

P ≤ 0.01 or 1% P ≤ 0.05 or 5% We want to be as sure as we can that the differences in our results are due to our IV and NOT chance! P is like Chance – Possibility! P is known as the Level of Significance Or a level of possibility that our results were due to chance

So with a significance level of P ≤ 0.05 we are 95% sure the differences in our results are due to the manipulation of our IV With only a 5% risk of them being due to chance So with a significance level of P ≤ 0.01 we are 99% sure the differences in our results are due to the manipulation of our IV With only a 1% risk of them being due to chance P ≤ 0.01 P ≤ 0.05

If our results are significant… We accept our directional hypothesis We reject our null hypothesis If our results are NOT significant… We reject our directional hypothesis We accept our null hypothesis

Finding Significance… Observed value: The value we get from our results (using a statistical test) Critical Value: The result we have to compare it to (See Page 582)

One or two tailed? One tailed: Directional Hypothesis Two tailed: Non-directional Hypothesis

What if we make a mistake… ooops! Type 1 Error ◦A null hypothesis is rejected when it should not have been ◦(our results were NOT significant… ooops!) ◦Optimism (O for one!) Type 2 Error ◦A null hypothesis is accepted when it should not have been ◦Our results were significant, but at a different level ◦We chose P ≤ 0.01, could have been significant at P ≤ 0.05 ◦Pessimism