Probability 6 mark question??! Can you do it?

Do "none work part time" and "1 works part time"

then think

Out of the "20" employees how many are part time?

9:11 = 20 people
1/3 male part time and 1/2 female part time

How many?? Sorry! I wish I was as good as you, but with your help I know i will one day get maybe close!

3 males are part time and 5.5 females are part time

How did you get that?

Out of the "20" employees how many are part time?

1/3 * 9

1/2 * 11

What's the final answer from the MS?

3 males are part time and 5.5 females are part time

THanks 1- 0.0119 -0.0706 =0.917



Ok so 3 males are part time and 5.5 females are part time. But you can't get 5.5 of a female?

If you can/can't, what is the next step to get 23/40???

Ok so 3 males are part time and 5.5 females are part time. But you can't get 5.5 of a female?

Well if 3 males and 5.5 females are part time, then 8.5/20 are part time, and 11.5/20 are not. This can also be 23/40 and 17/40 - you get the same answer. Then just plug it into your binomial distribution

It's important to note the question doesn't say there are 20 employees. That's just the ratio. So you have 5.5 females part time per 20 employees.

Cheers your a legend!



Oh right that makes so much sense now!

Where 17/40 = part time; 23/40 = full time...

$(\frac{17}{40} + \frac{23}{40})^8=[br][br]\displaystyle \binom{8}{7} \frac{17}{20} \left( \frac{23}{40} \right)^7 + \displaystyle \binom{8}{8} \left(\frac{23}{40}\right)^8 = 0.08260608613[br][br]1 - 0.08260608613 = 0.9173939139$
hope this isn't too late :P

No worries

Lol it's fine I did 1-po-p1 and got that answer! Thanks ( I am good at that, just knowing what they want is the longer part! )


I know this may sound really daft, but why would I divide 8.5/20 ??? I mean 8.5 is the part time workers, we worked that out from timesing it from the ration 9:11.....so why divide by 20?

1/3 * 9

1/2 * 11

What's the final answer from the MS?

Ah ok

If you look at the ratio you will see where the 20 comes from. The ratio is 9:11. This means there are 9 males for every 11 females. So, if we had 20 workers, 9 would be male, and 11 female hence 9/20 are male and 11/20 a female.

Now, a third of male work part time, and half of females work part time. A third of 9/20 is 3/20. A half of 11/20 is 5.5/20. So in total 8.5/20 work part time.

Does this explain what you wanted?

Oh ok, but then why did the above times by 9 and 11m if just did that? Why not do what you did?

They are both the same things essentially. However, he was just showing you how to get the numerator, assuming you would have known the denominator would be 20.
1/3 *9 and 1/2 *11, is the same as: 9/3 and 11/2. Both give you 3 and 5.5 to get your 8.5 numerator