UK USIndia

Magic for Learning and Revision

If an odd result is found, repeat the experiment.

# Unit 4 - Identifying Anomalous Results

Following the practical work in your experiment, the next step is identifying any anomalous results. In this GCSE Biology quiz we look at the effects of anomalous results, how to go about identifying them and what action we can take when we have found them.

Anomalous results are odd results - those which are not in keeping with the rest of the results or which do not follow any correlation you have spotted. If you have repeated your experiment several times, you will usually find fewer anomalous results than if you carry it out only once.

There can be many reasons for anomalous results. You may not have noticed that one of the control variables wasn't fully under control for that particular result. You may have added a little too much of something. You could even have written down the result incorrectly or mis-read it when transferring it from your notes to your report.

When commenting on anomalous results, always try to offer some sort of explanation e.g. "this result is much higher than those either side. This might have happened if I didn't control the temperature properly and it went higher during this part of the experiment".

There are two things that you can do with anomalous results. Firstly, if you have the time, you can repeat that part of the experiment, taking great care with quantities and making sure that the control variables are fully under control! Hopefully, a repeat of the experiment will give you a figure that fits with the pattern of the other results. The second thing that you can do is to simply not use them when drawing your conclusion. You may think that not using some of your results that don't fit the pattern that you have spotted is cheating. It isn't - anomalous results can make your conclusion unreliable especially if you are using numbers such as a numerical correlation of the independent and dependent variables. Professional scientists do this all of the time.

When writing up your experiment, it is really important to mention the anomalous results even if they don't appear in your final results table or graph/chart. It shows that you have worked carefully and are aware that experiments are not perfect. If you have been very careful and repeated the experiment several times, you may not have any anomalous results. In this case, simply mention in your evaluation that you can't see any anomalous results. That will tell the person marking your work that you are aware of the concept of anomalous results even if you didn't have any to comment on.

See how much you know about identifying anomalous results and what to do about them by playing this quiz on the subject.

1.
Anomalous results can be identified by looking at the...
equipment
results
method
hypothesis
Sometimes it is obvious from the numbers in front of you - other times, it only becomes obvious if you have plotted a graph or a chart of some sort
2.
If an anomalous result is included in the data, it will increase this.
Mean
Mode
Range
Median
The greater the range, the less certainty there is about the reliability of the conclusion
3.
After you have written your results into a table, what do you do next?
Identify anomalous results
Carry out a risk assessment
Do an evaluation
Go home
You may need to draw a graph or a chart to help you
4.
Which of these is the odd result?
2, 1, 2, 4, 3, 11
1
2
3
11
This one should have been easy to spot as it is so different from the rest
5.
What does anomalous mean?
Odd
Mean
Normal
Biased
An anomaly is something that does not fit the pattern
6.
Which of the following would be the best thing to do if an odd result is found?
Ignore it completely
Panic
Repeat the experiment
Take an average
You would repeat the experiment as many times as needed. Never ignore an anomalous result, the least you should do is to mention it in your evaluation
7.
Anomalous points on a graph do not follow the...
line of best fit
fashion
hypothesis
method
Graphs are very useful for identifying anomalous results. The odd result will be more out of line with the other points on the graph
8.
Anomalous results can be caused by...
using inaccurate measuring equipment
rushing the experiment
any of the above
Human errors of many types can contribute to anomalous results, but in an exam you cannot just state human error, you should try to be specific
9.
Anomalous results are...
always included in the calculation of mean (average)
excluded from the mean
included in the mean sometimes
crossed out
Bad data is still data. If there are anomalous results, the best thing that you can do is to repeat the experiment. When that isn't possible, discard them but ALWAYS state why you did that in the evaluation section
10.
Anomalous results can make the results...
more reliable
less reliable
the same
agree with the hypothesis
If anomalous results are included in a small sample size, they can make the result less reliable