Question

1) 72% of US households have Netflix streaming. Choose 5 households at random. What is the probability that at least 1 does not have Netflix streaming.

2) the area under the normal disttibution curve to the left of the mean is negative?

3) P(z>0) under a normal distribution curve is?

Answer 1

1)

Answer)

As there are fixed number of trials and probability of each and every trial is same and independent of each other

Here we need to use the binomial formula

P(r) = ncr*(p^r)*(1-p)^n-r

Ncr = n!/(r!*(n-r)!)

N! = N*n-1*n-2*n-3*n-4*n-5........till 1

For example 5! = 5*4*3*2*1

Special case is 0! = 1

P = probability of single trial = 0.28 (1-0.72) (as 0.72 have netflix so 0.28 does not have netflix)

N = number of trials = 5

R = desired success = at least 1

We know that sum of all the probabilities is = 1

So, P(at least 1) = 1 - P(0)

= 1 - 5c0*(0.28^0)*(0.72)^5-0

= 0.8065082368

2)

No area under normal curve to the left of the mean is = to the right of the mean = 50%

Because normal distribution is symmetrical about mean

3)

From z table, P(z>0) = 0.5 or 50%

As 0 is the mean of standard normal z table

And above and below mean in normal distribution 50% lies