NOTE THIS INFORMATION MAY BE IN CONFLICT WITH THE SENIOR SECONDARY GUIDES - THE SENIOR SECONDARY GUIDES WILL BE UPDATED SOON, THIS IS TO GIVE RELEVANT INFO URGENTLY TO TEACHERS WHO ARE LOOKING FOR CLARIFICATION. THIS IS THE NEW MATERIAL TO GO UP SOON.

What classifies a task as an experiment? There must be an intervention

Type of experiment: Comparison

Note 1: It cannot be a prediction-type task involving scatterplots. For example, dropping a ball at various heights, recording the bounce heights and then using these results to predict a bounce height from a drop height.


Type of Design
1. Two independent group comparison
(Note 2: do not use word sample, rather use the word group, and note two groups must be independent)

There must be random allocation to the two in an attempt to make the comparison fair. Students can discuss why.

Analysis: Compare using dot plots and/or boxplots

Students describe what they see. Use mean, sd. Describe variation, clusters etc.

Conclusion is descriptive: For example, these data suggest (appear) that using a fixed target line resulted in (caused) the students jumping further on average than when no target line was used.

Note 3: There are two types of inference: causal-type inference and sample-to-population type inference. The conclusion statement of an experiment at Level 2 must at least include a causal-type inference statement as above.

Note 4: A sample-to-population type inference only is not acceptable. For example, a conclusion written as “ these data suggest that (all) students with the target line tend to jump further than (all) students without the target line is not acceptable.




2. Paired comparison

Note 5: Paired comparison is where measurements are taken on the same person or object. You cannot do separate dot plots of before and after and discuss as if they were independent.

Analysis:New type of plot

Before Intervention
Experimentspaired.JPG
After Intervention


Students describe what they see only in terms of the direction of the arrows (i.e., the differences).

Followed by a plot of the differences.
Students describe what they see. Use mean, sd of the differences. Describe variation, clusters etc. of the differences.

Conclusion is descriptive: For example, these data suggest (appear) that the caffeine caused the pulse rate in the students to go up on average.

Note 6: For both types of experiment students can discuss other relevant factors that they should consider etc.

Note 7: Notes 3 and 4 above also apply to experiments with a paired comparison design.