OBJECTIVE
Conduct an experiment to compare the absorbency properties of two brands of paper towels by measuring the amount of water each can absorb.
DIRECTIONS
Appoint, with the agreement of the team members, one person who will always fold and dip the paper towel in the glass, and a second person who will read all the water measurements. One person in the group (it may be one of those listed above) will need to record the data for the group. Any other group members assist in the experiment and take notes.
Start by deciding how many measurements you will make on each brand. (A minimum of 4 is required.) After deciding, establish a randomization scheme which provides the order in which observations will be taken. Write down this number here:__________
When you are ready to start have the person assigned to the measuring duties put a known amount of water into the glass, measuring it carefully with the graduated cylinder. (About 10cm high works pretty well.) Have the person appointed to dip the paper towel describe the method by which they will insert the towel into the glass (are they going to fold it carefully first, or will they wad it up, or will they just kind of cram it in?). Write 1-2 sentences describing this process below:
Also have that person describe when they will remove the towel from the water (how long will they leave the it in, will they toss it out as wet as possible, will they let it drain a little, will they let it drain until it stops dripping?) Describe in 1-2 sentences below:
Now proceed with the first observation. As soon as the towel has been discarded, have the measuring person measure the amount of water left, and record the difference between this value and the initial amount of water as the amount absorbed by the towel.
Repeat this process, duplicating the conditions at each trial as nearly as possible. Record the data in two columns, one for each brand. Beside each observation record the observation number (1 for first, 2 for second, etc.). You may look back at these numbers later to see if there was any trend across time in the way you took measurements. Record your data here:
BRAND A BRAND B
Discuss with the group appropriate techniques for looking for differences in the absorbencies. First, make a graphical display of your data below. Does there appear to be a difference between the brands?
Next, decide which hypothesis test can be conducted to determine whether or not there is a difference between the absorbency of the two brands. Write down the null and alternative hypothesis below:
Now conduct the hypothesis test. Record your calculations below, and state your conclusions:
Based on your hypothesis test, does there appear to be a difference between the two brands of paper towel? Explain briefly.Discuss with your group any problems that came about in conducting this experiment. If you had the opportunity to redesign this experiment, what changes would you have made, and why? Items to think about: who carried out the experiment (same person each time?); how the experiment was conducted (same way each time?); how the measurements were made (was this accurate and consistent?); was randomization used?; are the paper towels you used in the experiment a representative sample of the whole population of paper towels from each of these two brands? What problems arose that you can prevent next time? Write a few sentences that talk about the design of your experiment in terms of the above questions.