1. Targeted Connections: Experimental Design and Data Analysis Margaret Buerman mbuerma@nwmissouri.edu Patricia Lucido plucido@nwmissouri.edu Cheryl Malm cgmalm@nwmissouri.edu Northwest Missouri State University

2. Scientific Methods  Observation –  No cause and effect methodology  Bird count, plant survey, genetic trait count  Correlation  Plant survey with observations of environment  Experimental Design  Define an independent variable, dependent variable and constants

3. Planning Experiments  8 Steps to the Plan  Starting with Cothron, Giese, Rezba’s Students and Research

4. What materials are available for experimenting with ____?  What materials / conditions are available for conducting experiments on yeast?  Growth nutrients  Temperature  Light conditions  pH of the medium Q 1

5. How can the available materials be changed?  How can the materials / conditions be changed to affect yeast?  Growth medium: % concentration of ingredients, liquid or solid  Temperature: constant, variable temp,  Light conditions: natural, artificial, time of exposure (UV sensitive vs normal)  pH: values from 4 to 8 Q 2

6. How do ____ act?  How do yeasts act?  Grow  Form colonies on solid medium  Change in turbidity in liquid medium  Form pigments Q 3

7. How can response to the change be measured?  For yeast  Count number of colonies  Change in turbidity  Observe color of colonies  Record shape of colonies  Observe changes in cell shape under microscope Q 4

8. The Experimental Design Plan The Effect of Sunlight on Yeast Growth  Possible Hypotheses H1: The longer the yeast are exposed to sunlight, the fewer the number of colonies. Ho: The mean number of yeast exposed to UV light will equal the mean number of yeast not exposed to UV light. Ho: The mean mass of yeast exposed to UV light will equal the mean mass of yeast not exposed to UV light.

9. What is the Experimental Plan?  Title  Hypothesis  Independent Variable  Control  Levels of the Independent Variable  Number of Trials  Dependent Variable  Constants

10. The Effect of Sunlight on Yeast Growth  The longer the yeast exposure to sunlight, the fewer the number of colonies formed. Independent Variable: The amount of sunlight 0 minutes (control) 5 minutes 10 minutes 15 minutes 3 trials 3 trials 3 trials 3 trials Dependent Variable: the number of colonies Constants: same pH, growth medium, temperature

11. What equipment and measurement tools are necessary?  Means of detection or measurement:  Eye  Microscope  Drying oven  Balance Q 5

12. What kind of data are collected?  Types of Data in terms of:  Discrete – only whole integers  number of yeast colonies  Continuous – divisible into partial units  dry mass of yeast  Types of Data in terms of:  Quantitative – plate counts, mass measurement  Qualitative – pigment color (nominal) Q 7

13. Quantitative Data  Scale of equal intervals that are continuous (or discrete)  Interval Level of Measurement  An arbitrary zero (C or F temperature)  Cut grass to same height, observe growth  Ratio Level of Measurement  An absolute zero (height, Kelvin temperature)  Height of the plants

14. Discrete Quantitative time m5101520 colonies100754530

15. Continuous Quantitative Data time min051015 Mass mg0.980.720.470.28

16. Discrete Data - Whole Integers Number of snails in the terrarium vs Time

17. Continuous Data  Scales that are divisible into parts.

18. Qualitative Data  Nonstandard scales of discrete or categorical data  The plants appear stressed or wilted  Leaf condition  Nominal Level of Measurement  No ranking (gender, eye color, plant variety)  Ordinal Level of Measurement  Ranked data (order in a race, line up from tallest to shortest)  Germination order 1 st, 2 nd, 3rd ….

19. What kind of data display is appropriate?  Scatter plots  Box and Whiskers  Histograms  Bar Graphs  Pie Charts  Frequency Distribution  Line Graphs Q 8

20. What Statistical Descriptions Are Appropriate?  Descriptive statistics  Central Tendency  Variation  Inferential statistics  t Test  Chi-Square Q 9

21. Descriptive Statistics for Data  The data’s central tendencies.  Mean  Median (not for nominal data)  Mode

22. Descriptive Statistics for Data  Measure of Variation or Spread  Range – quantitative data  Interquartile Range  Boxplot (Box and Whisker)  Frequency Distribution – qualitative data  Stem-and-Leaf Diagram  Standard Deviation

23. Data Description  Compare the Medians  Compare Boxes and Interquartile range  Describe Symmetry of the distribution  Describe Range of values  Mention Outliers  Hypothesis support

24. Inferential Statistics  Are the findings for a small sample likely to represent a larger group?  t Test  Chi square

25. The t Test (uncorrelated with equal sample size)  Use the t test to determine if the quantitative difference between the means is statistically significant. H1: The longer the yeast are exposed to sunlight, the fewer the number of colonies. H1: The longer the yeast are exposed to sunlight, the fewer the number of colonies. Ho: The mean number of yeast exposed to UV light will equal the mean number of yeast not exposed to UV light.

26. Chi-square test  Use the Chi-square (X 2 ) to determine if the differences between frequency distributions in qualitative data are statistically significant.  Ho: The frequency distribution of plant height is not significantly different from the frequency distribution predicted by chance

27. Chi-square test

28. Resources  Students and Research Cothron, Giese, Rezba ISBN 0-7872-6477-6  The Cartoon Guide to Statistics by Larry Gonick  Biological Experiments and Activities Integrating Mathematics by Stephen Rodecker and Jim Patzold  http://mathforum.org