# GCSE Biology Controlled Assessment watch

1. I am currently doing my practice controlled assessment in biology and am very unsure on how to draw my graph.
The experiment involved woodlice and a choice chamber. There were 10 time intervals, using four different moisture conditions, but I don't know what type of graph to draw because it seems that my range bars overlap too much making it unreadable.

2. What did you measure and what did you vary? Plot the thing you varied along the x axis (time) and the thing you measured (number of woodlice? I'm a bit confused about your experimental procedure...) on the y axis.

With range bars, at GCSE I believe you are told to plot them to show the full range of your results (i.e. going up the the highest and down to the lowest result for each time interval). You should also do horizontal error bars relating to the error in your time measurements (usually half the smallest time interval - so if you measured in seconds, do the error bar 0.5 seconds to either side).

You should plot a scatter graph showing your mean number of woodlice (or whatever it was you measured) against the time, then plot the error bars for each point as I said above. Don't worry about the error bars overlapping - you can talk about this in your evaluation, since it shows that there may not have been a significant difference between some of the results (since the error bars overlap - so the result could have been the same for both time intervals).

This may seem a bit weird, particularly the bit about plotting range bars from your minimum to maximum data points - since if you do more repeats your error bars will probably get larger. Don't worry too much about this - at A level you would be taught to use other methods of calculating the spread of results, such as the standard deviation - these typically involve dividing by something relating to the number of repeats (usually the square root of the number of repeats). However, at GCSE just stick to the method your teacher taught you

If the range bars overlapping makes it really hard to read the graph, you could consider using different colours - for example the crosses (data points) in red, the line of best fit in blue and then the error bars in green or something. Check with your teacher that this is ok though - particularly if it is for an assessment.
3. (Original post by dragonkeeper999)
What did you measure and what did you vary? Plot the thing you varied along the x axis (time) and the thing you measured (number of woodlice? I'm a bit confused about your experimental procedure...) on the y axis.

With range bars, at GCSE I believe you are told to plot them to show the full range of your results (i.e. going up the the highest and down to the lowest result for each time interval). You should also do horizontal error bars relating to the error in your time measurements (usually half the smallest time interval - so if you measured in seconds, do the error bar 0.5 seconds to either side).

You should plot a scatter graph showing your mean number of woodlice (or whatever it was you measured) against the time, then plot the error bars for each point as I said above. Don't worry about the error bars overlapping - you can talk about this in your evaluation, since it shows that there may not have been a significant difference between some of the results (since the error bars overlap - so the result could have been the same for both time intervals).

This may seem a bit weird, particularly the bit about plotting range bars from your minimum to maximum data points - since if you do more repeats your error bars will probably get larger. Don't worry too much about this - at A level you would be taught to use other methods of calculating the spread of results, such as the standard deviation - these typically involve dividing by something relating to the number of repeats (usually the square root of the number of repeats). However, at GCSE just stick to the method your teacher taught you

If the range bars overlapping makes it really hard to read the graph, you could consider using different colours - for example the crosses (data points) in red, the line of best fit in blue and then the error bars in green or something. Check with your teacher that this is ok though - particularly if it is for an assessment.
Sorry for being vague - yes I am measuring the number of woodlice.

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