BS 105 (Sections 01+ 02)                                                Plant Experiment Assignment

Use the class average data provided in the table to complete this assignment, with the exception of question #4.  There are two parts as follows: 

1.       Your responses to the questions given below.  Your answers to the questions MUST be typed and double-spaced throughout; failure to comply with these requirements willresult in a grade of zero.  Number your answers to correspond with the number of the questions.  You do not have to retype the questions!  Include your name and section number in the upper right-hand corner of your paper or your assignment will not be graded.

2.       Preparation of two graphs of the data.  Suggestions for preparation of the graphs are provided on the back of this page and will be discussed during lab. 

¨       The first graph should depict the effect of seed number on percent germination of the seeds.  (10 points)

¨       The second graph should depict the effect of plant number on mean biomass per plant.  (10 points)

¨       It is strongly recommended that you complete both graphs before you begin preparation of your answers to the questions.  

·         This is NOT a group assignment.  You MUST work independently in preparation of the graphs and typed responses.

·         Please staple your typed answers to your graphs.  The correct order should be typed answers followed by figure 1 (the first graph) and then figure 2 (the second graph).

1.       When conducting an experiment a researcher first states the hypothesis about how the experiment will turn out.  The hypothesis is typically stated as two possible outcomes, the null hypothesis (H₀) and the alternate hypothesis (H₁).  Based upon the data, the researcher will then accept one hypothesis and reject the other.  An example is given below.

·   A study was conducted of freshmen students to see if there would be an improvement in individual test scores when the students were placed in supervised study groups at the start of the semester.  Half of the students were assigned to study groups and half were not.

*         null hypothesis (H₀) = Placement in study groups will result in no improvement in student test scores

*         alternate hypothesis (H₁) = Placement in study groups will result in improvement in student test scores.

QUESTION:  For the experiment we conducted with the radish plants, clearly state the null hypothesis (H₀) and the alternate hypothesis (H₁), in a format similar to the example provided above.  Since we have two dependent variables in this experiment, you should have two null hypotheses and two alternate hypotheses.  (4 points)

2.       In a controlled experiment we can describe three types of variables: independent, dependent, and controlled.  Clearly identify the independent variable (only 1), dependent variables (only 2), and controlled variables (at least 3) in the radish plant experiment.  (6 points)

3.       On the basis of examination of the graphical data, which hypotheses do you accept and which hypotheses do you reject?  EXPLAIN your answer.  (4 points)

4.       If you examine the raw data closely you’ll notice some seemingly impossible results.  Offer a plausible explanation, and then identify at least two other sources of potential error during the experiment.  (2 points)

5.       The data collected allow us to draw a conclusion regarding intra-specific competition of radish plants.  Describe one “real world” situation where experiments like this could be helpful or informative.  In other words, describe how the results of this experiment could be applicable in the “real world”.  (4 points)

DUE DATE:          Monday, October 7^th, 2013, in lecture (9 a.m.)
GRAPHING DATA

                The class performed an experiment concerning intra-specific competition of radish plants.  You are to graph the data collected from that experiment.  You should have two graphs; one for the biomass per plant data and the second for the percent germination data.  You may either hand draw the graphs or use computer graphing software (e.g., EXCEL) to assist you.  Below are several suggestions to help you prepare high quality graphs.

1.     Decide whether you have “continuous” or “categorical” data.

            Continuous data can assume an infinite range of numerical values (e.g., temperature, distance, weight, etc.).  Categorical data fall into discrete categories (e.g., sex, blood type, political party, etc.).  Continuous data are best presented by line graphs and categorical data are best presented by bar graphs.

2.     If you hand draw the graphs, use graph paper for greater accuracy in plotting the data points.

            Graph paper is essential for hand drawing graphs.  The grid on the graph paper allows the accurate plotting of data points.  If you hand draw your graphs, you must use graph paper.

3.     If you hand draw the graphs, use a ruler.

            A ruler is an essential tool for hand drawing graphs.  When you draw in the axes and the lines of a line graph or the bars of a bar graph use a ruler or straight edge.  Unless you are a very good and steady artist it is very difficult to free hand a straight line.

4.     If you hand draw the graphs, draw in the axes.

            Do not rely upon the grid margin of the graph paper as your axes.  Too often, relying upon the margin of the grid will leave you with too little space for your axis labels.

5.     Use a good sense of proportionality.

            The x axis (abscissa) and y axis (ordinate) should be roughly equal in length.  Do not make the abscissa 5 cm long and the ordinate 50 cm long.

6.     Make good use of space on the sheet of paper.

            The graph should essentially fill the page.  Do not make a 5 cm x 5 cm graph in one corner of a sheet of paper that is 20 cm x 25 cm.

7.     Label the axes.

            The labels should clearly indicate what values are plotted on each axis (e.g., mean weight per plant).  The axis labels should also include the appropriate units (e.g., grams per plant).

8.     Include a title.

            A descriptive title is a vital part of any graph.  Tell the reader what data are being presented by the graph.  The title should be placed BELOW the actual graph and identified as “Figure X”, where the X represents the figure number (1, 2, 3, etc.).

9.     Use equal divisions along the axes.

            An equal space should be given to equal numerical values (e.g., 5, 10, 15, 20, 25 vs. 5, 8, 12, 19, 24).  Some graphing software will not allow you to appropriately divide the axes into equal units.

10.  Do not “smooth” the curves.

            Connect the dots for your true data points.  Do not guess or interpolate a hypothetical curve unless you have done the appropriate statistical calculations to fit the line.

11.  By convention, the dependent variable is plotted on the ordinate and the independent variable is plotted on the abscissa.

            The ordinate is the vertical Y-axis and the abscissa is the horizontal X-axis.  The independent variable is what you manipulate, while the dependent variable is what you measure to determine an outcome.  The dependent variable “depends” on values of the independent variable.

12.  BE NEAT!

                A very neat, clean, well-done graph leaves a good impression.  A graph that is all crumpled; covered with erasures, ink smears, or coffee stains leaves a bad impression.