S1 January 2007 Q6

(a) Give two reasons to justify the use of statistical models. (2)

It has been suggested that there are 7 stages involved in creating a statistical model. They are summarised below, with stages 3, 4 and 7 missing.

Stage 1. The recognition of a real-world problem.
Stage 2. A statistical model is devised.
Stage 3.
Stage 4.
Stage 5. Comparisons are made against the devised model.
Stage 6. Statistical concepts are used to test how well the model describes the real-world problem.
Stage 7.

(b) Write down the missing stages. (3)

Mark scheme (a)

Scheme	Marks
Used to simplify or represent a real world problem Cheaper or quicker or easier (than the real situation) or more easily modified To improve understanding of the real world problem Used to predict outcomes from a real world problem (idea of predictions)	B1 B1
	(2)

Notes

B1B1 (any two lines)

1^st B1 For one line
2^nd B1 For a second line
Be generous for 1^st B1 but stricter for B1B1

Mark scheme (b)

Scheme	Marks
(3 or 4) Model used to make predictions. (Idea of predicted values based on the model)	B1
(4 or 3) (Experimental) data collected	B1
(7) Model is refined.	B1
	(3)
	(5 marks)

Notes

1^st & 2^nd B1 These two points can be interchanged.
Idea of values from (experimental) data and predicted values based on the model.

1^st B1 for predicted values from model e.g. “model used to gain suitable data”

2^nd B1 for data collected. Idea of experimental data but “experiment” needn’t be explicitly seen

3^rd B1 This should be stage 7. Idea of refinement or revision or adjustment