Practise A Level probability, population estimates, diversity indices, variation measures and significance tests, then translate outputs into biological conclusions.
Phenotypic variation exists in natural populations. There are many causes of variation. Natural selection determines which phenotypes are advantageous.
There is variation in the quantity of vitamin D stored in the body.
Vitamin D has an important role in keeping bones healthy. The main storage form of vitamin D in the body is serum 25-hydroxyvitamin D (serum 25-OHD).
A study was carried out on 262 healthy women to investigate if the concentration of serum 25-OHD varied between summer and winter. The women had taken no vitamin D supplements. The age range of the women in the sample was 40 to 72 years old.
Table 5.2 shows the results of the study.
Table 5.2
Additional analysis showed that there was no significant correlation between age and serum 25-OHD concentration.
Explain what is meant by standard deviation.