A characteristic can show either discontinuous or continuous variation. Table 5.1 lists statements that apply to discontinuous variation, continuous variation, or both. Fill in both columns of Table 5.1. Place a tick (✓) in the box if the statement applies, and leave the box blank if it does not.
Explain what standard deviation means.
The $t$-test was used to compare the mean concentration of serum 25-OHD in summer with the mean concentration of serum 25-OHD in winter, as shown in Table 5.2. Calculate $t$ using the formula given: $t = \frac{|\bar{x}_1 - \bar{x}_2|}{\sqrt{\left(\frac{s_1^2}{n_1} + \frac{s_2^2}{n_2}\right)}}$. Give your answer to four significant figures.
The critical value at the $0.0001$ probability level is 3.773. State the conclusion that can be drawn from the results of the study shown in Table 5.2, and explain how the answer to your calculation in (b)(ii) can be used to support this conclusion.
Suggest the most likely causes of variation in the amount of vitamin D stored in the body in this sample of women.
The critical value at the $0.0001$ probability level is $3.773$. State the conclusion that can be drawn from the results of the study shown in Table 5.2, and explain how the result of your calculation in (b)(ii) can be used to support this conclusion.
Suggest the most likely causes of variation in the amount of vitamin D stored in the body in this sample of women.