Look at the individual value plots of your own repeated measurements of the same

Question

Look at the individual value plots of your own repeated measurements of the same object with different instruments (data A for shells, B for worms). A big difference in mean between instruments for the same object would indicate an accuracy problem for one or both of the instruments, and a large amount of scatter around a mean indicates low precision. Based on these graphs, did you have problems with either accuracy or precision? Which?

(please provide an explaination to your answer, as I want to understand how to approach such graphs).

Explanation / Answer

We have been taking repeated measurements using the following two instruments

1) Caliper 2) Ruler

If we observe the readings from Ruler on the Graph 1(shells) and Graph 2(worms), we can clearly see the observations having two dots or two set of observations at many points which should be counted seperately.

For Graph1(worm) the following points are there

Ruler : 84 86 86 87 89 Mean= 86.4 Caliper : 83.2 83.8 85 85.4 85.6 Mean= 84.6

Note: Mean= Sum of all the observations/ Total no. of observations The above data points are approximate of what is represented in the graph.

From the above observations we can observe there is a significanct difference between the means of the two instruments which means we have might have accuracy issue associated with the instruments.

For Graph2(shell) the following points are there

Ruler : 14 15 15 16 16 Mean= 15.2 Caliper : 14.3 14.8 15 15.5 16.4 Mean= 15.2   

Note: Mean= Sum of all the observations/ Total no. of observations The above data points are approximate of what is represented in the graph.

From the above observations we can observe there is no significant difference between the means of the two instruments which means we have no accuracy issue associated with the instruments. so for the deviations in mean in the first graph(worms) which is due the Precision of the instruments.

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