# Percentage points table (New A Level)

Discussion in 'Mathematics' started by mike372, Dec 27, 2017.

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1. Hi,

In the official Edexcel Year 2 textbook they have an exercise (3C) where they ask students to e.g. "use the percentage points table to find...". Any question that can be solved using the tables can also be done using a calculator so is there any disadvantage to not teaching students about the percentage points table? For example, could an exam refer to the table?

Thanks.

2. Since the percentage points table is given, and it's so quick, I would definitely get students to practise using it. However it only gives z-values for the standardised Normal, and students don't need to standardise any more, so it's a bit of a dead end. Calculator is the way to go, and questions will have to allow any acceptable method.

3. Thanks!

Are you sure students don't need to standardise anymore? There are lots of questions in the Edexcel textbook that seem to require it e.g.

X~N(mu, 3^2)

Given that P(X > 20) = 0.2

Find the value of mu.

Can this be done without standardising? I know you still don't need tables to solve it. There is a whole exercise with these types of questions.

4. I agree re encouraging calculator use but I don't agree with Adam re students not needing to standardise.

I think understanding the link between the standard normal and normal distributions is essential and should be taught - even if it is not going to be explicitly examined.

(What about finding the mean and std deviation given 2 known probabilities? Although I am not sure if this is still on the edexcel spec it certainly requires use of the formula for standardising)

5. Exactly they need to know it. calculator will give x value if mu and sigma are known otherwise you must work with z.