Statistics 1 Revision Notes - Mr Barton Maths

⇒
b =
= .
. = 1⋅773584906
⇒ a = – b = 5⋅00 – 1⋅773584906 × 2⋅50 = 0⋅5660377358
⇒ regression line equation is y = 0⋅566 + 1⋅77x to 3 S.F.
(b)
a is the cost in £1000 of reconditioning an incinerator which has not been used, so
the cost of reconditioning an incinerator which has not been used is £566.
(a is the value of y when x is zero)
b is the increase in cost (in £1000) of reconditioning for every extra 1000 hours of
use, so it costs an extra £1774 to recondition an incinerator for every 1000 hours of
use. (b is the gradient of the line)
9 Discrete Random Variables
Random Variables
A random variable must take a numerical value:
Examples: the number on a single throw of a die
the height of a person
the number of cars travelling past a fixed point in a certain time
But not the colour of hair as this is not a number
Continuous and discrete random variables
Continuous random variables
A continuous random variable is one which can take any value in a certain interval;
Examples: height, time, weight.
Discrete random variables
A discrete random variable can only take certain values in an interval
Examples: Score on die (1, 2, 3, 4, 5, 6)
Number of coins in pocket (0, 1, 2, ...)
Probability distributions
A probability distribution is the set of possible outcomes together with their probabilities,
similar to a frequency distribution or frequency table.
14/04/2013 Statistics 1 SDB 33