Data analysis and evaluation

Sample questions

Original practice questions written in the style of the exam.

1. Question 13 marks

   Students measured the time for amylase to break down all the starch in a sample at pH 7.

   Repeat	1	2	3	4
   Time / s	42	45	71	43

   (a) Identify the anomalous result.

   (b) Calculate the mean rate of reaction in $\text{s}^{-1}$, excluding the anomaly. Give your answer to 2 significant figures.

   Mark scheme

   • (a) $71\,\text{s}$ (repeat 3) (1)
   • (b) Mean time $= (42 + 45 + 43) \div 3 = 43.3\,\text{s}$ (1)
   • (b) Rate $= 1 \div 43.3 = 0.023\,\text{s}^{-1}$ (1)
2. Question 24 marks

   A student tested the tensile strength of fibres from two plants. She recorded the mass needed to break each fibre.

   Plant	Mean mass to break fibre / g	Standard deviation / g	Number of fibres
   P	312	85	5
   Q	286	79	5

   She concluded that fibres from plant P are stronger than fibres from plant Q. Evaluate her conclusion.

   Mark scheme

   • The mean for P is higher than for Q, which supports the conclusion (1)
   • But the standard deviations are large and the ranges of mean ± SD overlap a lot (1)
   • So the difference may be due to chance / may not be significant (1)
   • Only five fibres were tested, and fibre length or diameter may not have been controlled (1)