whats the formula for MEAN when working with grouped frequency?

[mizzy_893]

let me give the full question:
its called GROUPED FREQUENCY

can you please help me figure out how to work out mid-interval and frequency x mid interval.

SPEED(km/h) 40≤ s <45 45≤ s<50 50≤ s <55 55≤ s <60 60≤ s <65

FREQUENCY 4 8 10 7 3

MID-INTERVAL

FREQ X MID-
INTERVAL


A) complete table and estimate mean
B) how many skiers were travelling at less than 55km/h?
C) how many skiers were travelling at 50km/h or faster?

can someone tell me the formula for mean.

[StuartS]

The formulae is

Estimated Mean = Sum of(midpoint of each interval x frequency) / total frequency

Does that help?

[Maths_Tutoring]

A) The Mid interval can be calculated by calculating the middle point of the boundaries given.
For 40≤ s <45, the lower boundary is 40 and the upper boundary is less than 45 (but we still use 45 to calculate the mid point value, since its still a boundary. so (40+45)/2 would give you the first mid interval point

To calculate the Frequency X mid-interval, multiply the frequency by the mid-interval
So your first point would be 4*((40+45)/2)

B) Should be easier enough for you to work out, just sum the number of all those that are less than 55. (A hint, one of the columns ends in <55)

C) Once again, sum all those above 55≤


So as stuart said above, once you have the list of Frequency X mid-intervals Sum them up, and you can divide this number by the total frequency

[mizzy_893]

thank you so much for your help.thanks alot :)