T TEST

1 EJC H2 Biology T2W4 Biostatistic – t test Student’s t test 1. Introduction The main reason for carrying out observations and experiments in Biology is to test an idea or hypothesis; Biology, as a science, is an on-going subject, answers to one question, usually leading to further questions. Such work requires data sets. What we want to know is whether the data supports the initial hypothesis or not; does the data en able us to accept our hypothesis as a valid explanation or do we have to modify the hypothesis, or even reject it? You have already been introduced to one statistic al test that is used to analyse data sets – the ch i- squared test or Χ2 test. We will look at another test – the t test, in this lecture set. 2. Learning Outcomes (a) Able to apply t-test in Biological situations (b) Able to calculate standard deviations (c) Able to test for significant differences between means of two small unpaired samples Use the knowledge gained in this section in new situations or to solve related problems 3. References Gavin, J.W., Skills in Advanced Biology – Dealing with Data I Contents 1. Introduction ............................................................................................................... 1 2. Learning Outcomes.................................................................................................... 1 3. References ................................................................................................................. 1 4. Tests of Significance .................................................................................................. 2 5. Null Hypothesis, H0 .................................................................................................... 2 6. Χ2 test vs t test…………………………..………………………………………………………………………….2 7. Normal Distribution Curve……………………………………………………………………………..………3 Standard Deviation………………………………………………………………………………………….4 8. History of Student's t test………………………………………………………………………………………4 9. Calculating the t value..….……………………………………………………………………………………..6 Barnard, C., Gilbert, F. & McGregpr, P. - Asking Questions in Biology, 2nd Edition. T Test as a Parametric statistic - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4667138/ Bread and Butter of Statistical Analysis: T Test - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4744321/ Statistics: A Brief Overview - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3096219/

2 EJC H2 Biology T2W4 Biostatistic – t test 4. Tests of Significance Biological data is variable. It consists of small samples taken from large populations. Even though these samples are randomly chosen it is very unlikely that the data will conform exactly to the hypothesis. To overcome this problem, tests of significance are used to determine whether the data conform to the hypothesis sufficiently closely for a decision to be made, not only about the samples but also about the general pop