Download Answers: Vital Statistics: Averages and dispersion

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www.hoddereducation.co.uk/biologicalsciencesreview
Volume 29, Number 4, April 2017
Answers
Vital statistics: Averages and
dispersion
Dan Foulder
Here are the answers to the practice question on page 40 of the April 2017 issue:
Mean
(4.7 + 4.4 + 5.8 + 5.4 + 4.9 + 5.2 + 6.1) ÷ 7 = 5.214285714 = 5.21 (2 d.p.)
Median
Arranging the values in order:
4.4
4.7
4.9
5.2
5.4
5.8
6.1
The median value is 5.2
Range
6.1 – 4.4 = 1.7
Standard deviation
Red blood cell count/million
cells per microlitre
4.7
4.4
5.8
5.4
4.9
5.2
6.1
Deviation from the mean
−0.5143
−0.8143
+0.5857
+0.1857
−0.3143
0.0143
+0.8857
Squared deviation from the
mean
0.2645
0.6631
0.3430
0.0345
0.0988
0.00020
0.7845
(Note: the sum of the deviations from the mean is only zero here if you use many decimal places in
your calculation.)
Sum of squared deviations from the mean = 2.1886
s2 = 2.1886 ÷ 7 = 0.3127
s = 0.5592 = 0.56 (2 d.p.)
Hodder & Stoughton © 2016
www.hoddereducation.co.uk/biologicalsciencesreview
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