This lesson guides students through the use of the chi-squared test to determine the significance of the difference between observed and expected results. It is fully-resourced with a detailed PowerPoint and differentiated task worksheets that have been designed to cover the part of point 7.1 of the AQA A-level Biology specification which states that students should be able to use the test to compare the goodness of fit between the observed phenotypic ratios and expected ratios.
The lesson has been written to include a step-by-step guide that demonstrates how to carry out the test in small sections. At each step, time is taken to explain any parts which could cause confusion and helpful hints are provided to increase the likelihood of success in exam questions on this topic. Students will understand how to use the phenotypic ratio to calculate the expected numbers and then how to find the critical value in order to compare it against the chi-squared value. A worked example is used to show the working which will be required to access the marks and then the main task challenges the students to apply their knowledge to a series of questions of increasing difficulty.
This is the final lesson of topic 7.1 (inheritance) and links are made throughout the lesson to earlier parts of this topic such as dihybrid inheritance as well as to earlier topics such as meiosis.