Often, statistical errors are made inadvertently by researchers, with no intent

Question

Often, statistical errors are made inadvertently by researchers, with no intent to mislead. Each of the following statements contains a statistical error. Identify the error and provide a correct interpretation (4 marks).

A. In a study of the effect of DDT on the hatching success of raptors, the study team observed that after a decrease of 75% in hatching success (number of live births/number of eggs laid) in the 1970’s, the hatching success rate then increased by 80% after the banning of DDT. They concluded that the bird population had made a full recovery.

B. In the clinical trial of a revolutionary new blood pressure drug, the researchers observed blood pressure reductions in 35% of women and 43% of men. Their media release stated that 78% of participants experienced a decrease in blood pressure.


3.4. A health geography student was studying the wait times at two walk-in clinics (Clinic A & Clinic B). The table below gives the time (in minutes) that it took each patient to see the doctor for the two clinics

Clinic A 26 15 30 19 23 35

Clinic B 20 20 22 30 28 22

B. Clinic B claims that they have shorter wait times than Clinic A and are more consistent in the wait times. Using your best judgement do you think this claim is correct? Why or why not? (2 mark)

Explanation / Answer

Solving question 1

a) The final bird population in the end is (1-0.75)(1+0.80)= 0.45 or 45% of initial population only Hence, there is no full recovery.

b) 35% of women and 43% of men does not add to a total of 78% for all. The final percentage will be equal to

[35% * x + 43%*(1-x)] where x is less than 1 and refers to the proportion of women in total population.

The final percentage will be between 35 and 43

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