Question

At a certain airport, 75% of the flights arrive on time. A sample of 10 flights is studied. (Assume flights either arrive on time or delayed.)

Type your answer with 3 significant digits if necessary. (2.333, 0.0332, 0.000322).

a) What is the probability that at least 8 flights arrive on time?

b) What is the probability that 7 flights on time and 3 flights are delayed?

c) What is the standard deviation of the number of flights on time?

Answer 1

Probability of fight arrives on time ( P ) =75% = 0.75

number of trials ( n ) =10,

a)

x= 8

we want to find P(x 8)

formula is

P(x 8) = P(x=8) + P(x=9) + P(x=10)

P(x 8) = 0.2816+0.1877+0.0563

P(x 8) = 0.5256

Rounding to 3 decimals

Probability = 0.526

b)

we want to find P(x =7)

formula is

P(x =7) = 0.2503

Rounding to 3 decimals

Probability= 0.250

c)

formula for standard deviation is

=

=

= 1.3693

Rounding to 3 decimals

Standard deviation = 1.369