AS AQA Mathematics Statistics 1B MS1B June 2014

Hi guys, does anyone know whether we have to learn any equations for this exam or can they all be found in the formulae booklet? Thanks

how do you go about answering a questions saying - calculate the prob: whether its A or B but NOT both. I know how to do it for when it both and tried the reverse but............

P(A or B but not both) = P(A only) + P(B only)
or alternatively
P(A or B but not both) = 1 - P(neither A nor B) - P(both A and B)

Assuming only two, independent, variables.

I don't know how to explain it better than this without numbers... do you have an example?

(Also, stats is not my strong point, please correct me if I'm wrong!)

I don't think this is quite right, because P(AuB) = P(A) + P(B) - P(AnB), so your formula would be 2P(AnB) too much, so it would be P(A) + P(B) - 2P(AnB), or iff independent P(A) + P(B) - 2P(A)P(B)

Note: Although you may mean P(B') for your P(only A) and P(A') for your P(only B), and I'm still not sure if this would work...

Second note: Stats is my worst module by far as well, so I could be wrong! :L
Posted from TSR Mobile

Can someone help me with 7bi please?

hey guys

how do you find out how reliable an estimate (one which you have found using the least squares regression line) is when they say that the values of the residuals lie between approximately x and y?

If you look at a normal distribution graph:



you can see that there are likely to be some values at μ - 2σ and beyond - however, in this case, μ - 2σ is 37 - 25 * 2 = -13, which is negative. As the times in the context in this question cannot be negative, they are unlikely to be normally distributed.

z = (x - mu) / sigma

So that's the x value minus the mean, all divided by the standard deviation.


Edit: z = (x − μ) / σ

Can you not just use the tables to find z? Or is this equation for something different?

Posted from TSR Mobile

This equation is to find the z value, and then use that value on the normal distribution table to find the probability for that z value.

The tables find the probability USING the z value, not the other way around.

Okay thanks, so μ - 2σ is something I need to remember for the exam? And if there's a question on normal distribution use that?


Posted from TSR Mobile

No, it's not a general thing, it only works in this particular case. I just picked the number of standard deviations that first gave a negative number. It's very rare for a question like this to come up, but you should be familiar with the fact that most of the data in a normal distribution lies within about 3 standard devations either side of the mean.