Research Methods for the Biosciences: Interactive Exercises

Table of Contents

1. CHAPTER 1: WHERE DO I BEGIN?
2. CHAPTER 2: EXPERIMENTAL DESIGN
3. CHAPTER 3: WHAT TO DO WITH RAW DATA
4. CHAPTER 4: AN INTRODUCTION TO HYPOTHESIS TESTING
   1. Exercise 1
   2. Exercise 2
   3. Exercise 3
   4. Exercise 4
5. CHAPTER 5: HYPOTHESIS TESTING: DOES MY DATA FIT AN EXPECTED RATIO?
6. CHAPTER 6: HYPOTHESIS TESTING: ASSOCIATIONS AND RELATIONSHIPS
7. CHAPTER 7: HYPOTHESIS TESTING: DO MY SAMPLES COME FROM THE SAME POPULATION? PARAMETRIC DATA
8. CHAPTER 8: HYPOTHESIS TESTING: DO MY SAMPLES COME FROM THE SAME POPULATION? NON-PARAMETRIC DATA
9. CHAPTER 9: RESEARCH, THE LAW AND YOU
10. CHAPTER 10: REPORTING YOUR RESEARCH

CHAPTER 4: AN INTRODUCTION TO HYPOTHESIS TESTING

In this section we have included some additional examples for you to test out your understanding of the topics in this chapter. The areas each exercise covers are explained at the start of each question so that you can decide if this is a topic you would like to practice. Cross referencing to the book uses the numbers from the sections in the book. Cross referencing to material on these web pages is always indicated by a W. Throughout these sections we have highlighted the words that appear in our glossary. This is provided as part of this web site to make it easy for you to check the meaning of these terms.

In this chapter there are no calculations that need to be expanded or demonstrated in Excel , SPSS or Minitab. We do include a few interactive exercises. These are designed to give you further practice in choosing the correct statistical test and writing hypotheses.

Notes on choosing the correct statistical test

You will need to choose statistical tests either when you are designing an experiment or when one has been designed for you and you need to evaluate the data.

1. When designing the investigation.

In Chapter 2 we took you through how to select the most suitable statistical test for your hypotheses when designing an experiment.

First you determine if you are intending to test hypotheses. Then you decide what type of hypotheses these are likely to be. Though this may not be clear at the planning stage, it generally is.

Your next step is to determine if the data are likely to be parametric. We gave 5 criteria in BOX 3.2 to help you make this decision. For a few investigations where you know you will have numbers of things or counts or a ratio or proportions you can tell with some confidence that your data will be non-parametric. For other investigations however you will only be guided by the first criteria - 'will you be using an interval scale of measurement'? If your answer to this question is yes then we suggest that you assume you have parametric data and that you confirm this after the investigation has been carried out. If your answer is no then you have non-parametric data and should examine non-parametric tests.

Having decided if your data are likely to be parametric or not you should then be able to refer to the information at the start of the appropriate chapter. Here you make your decision based on the number of treatment variables, categories and observations. You should know this information from your draft planning. This takes you to the most probable statistics test.

The criteria for each test are given in the chapters. You can check these. There will always be some that cannot be confirmed until you have collected your data. None the less you should be able to establish that you have probably selected the correct test for your design. You may also decide at this stage that you need to modify your experimental design so that it meets the criteria for the statistical test.

2. When analysing data.

If the experiment has already been designed for you, as is common with most practicals, then you will already have your data and can use this to help you choose your test. The steps to follow are the same as those outlined in point 1.

First are you carrying out an experiment and wish to test hypotheses? If so which type of hypotheses?

From this you can use the information in appendix b to help you choose a test based usually on the number of treatment variables etc.

Finally check that you have chosen the correct test using the specific details in the chapter.

INTERACTIVE EXERCISE 1. EXAMPLE W4.1. Microbial counts of prepared sandwiches.

This exercise is based on research carried out by an undergraduate. The topics covered are those in 4.1 and appendix b.

INTERACTIVE EXERCISE 2. EXAMPLE W4.2. Levels of bioavailable heavy metals in sediments of a rural and an urban stream.

This exercise is based on research carried out by an undergraduate. The topics covered are those in 4.1 and appendix b.

INTERACTIVE EXERCISE 3. EXAMPLE W4.3. The sublethal effects of copper nitrate on the freshwater mollusc Lymnaea stagnalis.

This exercise is based on research carried out by an undergraduate. The topics covered are those in 4.1 and appendix b.

INTERACTIVE EXERCISE 4. EXAMPLE W4.4. The inheritance of coat colour in horses.

This exercise is based on research carried out by an undergraduate. The topics covered are those in 4.1 and appendix b.