S1 June 2011 Edexcel - Model answers and common questions in the FIRST POST

Tip - An obvious one. Learn how to use your Stats mode on your calc to check your answers.

It can work out measures of location and dispersion.

If you enter the data for a frequency table, it will calculate all the sums (x, x^2); it will also calculate the mean and standard deviation (but not median or quartiles etc).

You can enter a bivariate table and it will calculate all of the sums (x, X^2, y, y^2, xy); it will calculate PMCC and the values of a and b in the least squares regression line.

The Casio 991ES can also do some normal distribution calculations.

Model Answers

Hi arsey,

if i click stat mode i get a load of options.

If, for instance, i choose option (2) = a+bx then is this the regression line mode? when i click it i just get a table of x with a table of y next to it. How do i get it to be of use.

thanks again

Activate state mode for a list of options on your calculator (doing this from memory, so please excuse any minor mistakes)

The list of options contain things such as 1-Var (the variance setting) and A+Bx (regression line)

Selecting the 1-Var setting gives you a table with X values - input them and then press AC. Then press Shift-1 to enter stat functions using your previously tabulated information.

Shift-1 gives you a few options, and heres what they do -

Type-change type of date
Data-edit table
Sum-Sigma X squared and Sigma X
Var - Have a guess.

If you had chosen the regression setting in the orignial list, you would get two tables X values and Y values, because it is regression, and then if you had chosen Shift-1, you would get the following options

Type-Same as before
Data-Same as before
Sum-All your Sigma Xs and Ys
Var - All your Var, means and Standard Deviation stuff
Reg - Regression stuff, you want option 3, the 'r' value

you are a legend, thanks! I don't get the last point though (probably because i'm thick), what do you mean by the 'r' value...i see it on the calculator but for regression don't you just need a and b? What does r tell u?

Also can your calculator also find variance from grouped data
thanks

You are a legend, thanks! I don't get the last point though (probably because i'm thick), what do you mean by the 'r' value...i see it on the calculator but for regression don't you just need a and b? what does r tell u?

also can your calculator also find variance from grouped data
thanks

Question:
The random variable X ~ N(mean, sigma^2)
The lower quartile of X is 25 and the upper quartile of X is 45.
Find the value of mean , and the value of sigma

I dont understand how one would do this question systematically?
thanks!

You are a legend, thanks! I don't get the last point though (probably because i'm thick), what do you mean by the 'r' value...i see it on the calculator but for regression don't you just need a and b? what does r tell u?

also can your calculator also find variance from grouped data
thanks

I dont know if i'll want to check, if I realise i failed it'll kill the rest of my holiday.

Tip - An obvious one. Learn how to use your Stats mode on your calc to check your answers.