Is it a fair test?

Read the information about the investigation and decide whether the students have correctly applied a "fair test". If they have, record "true", if they have not, record "false".

Question 1

Students wanted to see if reward or punishment worked best when training puppies. One student brought in her puppy and a group of students took it for a walk. When it walked beside them they gave it a treat. It did not get a treat when it pulled on the lead. The next day another student brought in his puppy. They took it for a walk but this time when it pulled on the lead they spoke sternly to it and when it walked beside them they ignored it. The next day both puppies were brought in and taken for walks. They counted how many times each puppy pulled on the lead. Is this a fair test?

  1. TRUE
  2. FALSE
Feedback:
  1. At first this looks pretty fair but there are some big problems. Students should have done a lot more background research into methods of training puppies. How good was each puppy at being led before the investigation started? Maybe they did not try their method for long enough to have a reasonable expectation of achieving a fair result. One puppy was left for one day before being tested, whereas the other puppy was tested the next day- is this fair? This investigation needed to be replicated to be able to give a fair result- puppies may be different in age, temperament and many other aspects of their experiences.
  2. Correct. There were a lot of variables that were not controlled. Replication was needed.

Question 2

Students wanted to see if and "energy plus" battery lasted longer than a "El cheapo" battery. They put the "energy plus" battery into a torch and turned in on and recorded the time. The next day when they came to school they discovered that the torch was not working, so they recorded the time and calculated how long the battery lasted. They then put the "El cheapo" battery into a small portable fan and turned it on and recorded the time. When they came back after lunch they notice the fan had stopped working so they recorded the time and calculated how long the battery lasted. Is this a fair test?

  1. TRUE
  2. FALSE
Feedback:
  1. Incorrect. They have not controlled the variables. Both batteries should have been tested in the torch or both in the fan. They have also not been careful with their measurements. This experiment needed better planning.
  2. Correct. Not only were the variables not controlled and the investigation not replicated for reliability, but the timing was not accurate. This investigation needed a lot more careful planning.

Question 3

Students wanted to reduce the amount of litter left in the school playground. Every day for a week after lunch they collected all the litter and measured its mass. They then ran a campaign with posters, announcements and a competition to raise awareness and try to change behaviour. Two weeks after the campaign they repeated their litter collection and measurement. Is this a fair test?

  1. TRUE
  2. FALSE
Feedback:
  1. You have recognised that the students uses aspects of the scientific method to see if their anti-litter campaign was effective. They started with a problem and their "testable question" was "can a campaign to raise awareness of litter problems help to reduce the amount of littering?" It was good that they assessed the litter over five days rather than just one day. Their investigation plan did not help them to understand which, if any, of their campaign components was effective. Ideally they would test the effectiveness over a number of weeks to see if the effect of the campaign wore off. Maybe they could have deepened their understanding of the problem by conducting a survey.
  2. You have recognised that the investigation plan was not based on a clearly stated hypothesis. The investigation design did not allow the students to draw a valid conclusion about which aspect of their campaign had any impact, but because they did measurements over a number of days before and after the campaign, they could make a reasonable judgement about whether litter was reduced. Presumably the students would have tried to control other variables such as school attendance for both weeks i.e not choose one week when all of year 6 was on an excursion for the week.

Question 4

Students wanted to investigate whether take-away foods made you fat. They all measured their weight and then had a take-away meal. Some had fish and chips, some had pizza, some had hamburgers. They then measured their weight again and concluded that fish and chips makes you put on more weight than pizza. Is this a fair test?

  1. TRUE
  2. FALSE
Feedback:
  1. Incorrect. There are many reasons why this is not a fair test. If students had done background research they would have realised that digestion does not occur instantly and that weight gain is a slower process that occurs over a period of time. They did not control the quantity of food (or drink) taken in for the various types of take away foods. Other investigative methods such as a survey may give more information about people's eating habits and their weight.
  2. Students have not controlled variables and have not conducted the investigation over a reasonable length of time.

Question 5

Students wanted to find out if "blotto" was a better paper for absorbing spills that "sucko". They spilt one cup of water on the floor and tested how many sheets of each paper towel it took to absorb the liquid. Is this a fair test?

  1. TRUE
  2. FALSE
Feedback:
  1. Mostly true. They have done a good job at controlling variables because they used exactly the same amount of water each time. They could have made it better by making it really clear that the water was spread over the same area. They also need to make it clear how dry each patch of floor was after the spill was cleaned up. One good way of overcoming these small variations in how we do things is to replicate the activity and average the results. If their hypothesis was that cheaper paper towel is less effective than more expensive paper towel, they would also need to compare the number of sheets of towel in each purchase and the area of each sheet.
  2. Incorrect there are some key aspects of a fair test in the design. The test is fair because they used exactly the same amount of water but it still could be made a lot fairer. Firstly they need to replicate the results as different students may wipe up the spill to different standards. They need to indicate did they wipe the floor or just use the paper as a blotter. Maybe they could make it more precise by measuring the increase in mass of the paper towel as a gauge of how much water it had absorbed.

Solution

© State of New South Wales, Department of Education and Training 2008