00:01
In this question, we're given that 20 % of potential customers who walk into a particular clothing store will make a purchase.
00:08
And 20 customers who walk into the store are randomly chosen.
00:12
I'm going to let x be the number of customers who walk into the store are these 20 who will make a purchase.
00:18
So x will follow the binomial distribution, where n, the number of trials will be 20.
00:25
Since there are 20 customers, there will be 20 trials.
00:27
In this trial, we're looking at whether a customer made a purchase or not.
00:31
And p, probability of success in a single trial, that is probability of a customer who want to store and buying something, that'll be 20 % or 0 .2 in decimal.
00:44
So, n is 20, p is 0 .2.
00:49
Hence, probability x equals to r, where r is the number of customers, out of these 20 who are made a purchase.
00:56
That will be 20 choose r, 0 .2 to power of r.
01:00
And 1 minus 0 .2 is 0 .8 to the power of 20 minus r.
01:06
Then part a, we want to find probability exactly 10 of the customers will make purchase.
01:12
So we are looking at probability x equals to 10.
01:16
So just sub 10 into the bar.
01:29
And we get this.
01:36
And that would be 0 .00203, three significant digits or three significant figures.
01:44
Synchronous digit is the same as significant figures.
01:47
So 3sf.
01:49
Now in b, we want to find probability at least two of the customers make purchases...