A2 math help plz

[saloom987]

does any one have june 01 statistic 1 markscheme????????????

if no can you try and solve this question

When choosing a salad 60% of people choose a cheese salad. Use a suitable approximation to find the probability that, out of a group of 130 people, 90 or fewer will choose a cheese salad.

plz someone help me :?

 

[zarajay]

total number of people=n=130
P(choosing a cheese salad)= p = 60% = 0.6
P(does not choose a cheese salad)= q = 1-p = 0.4

mean=np=130 x 0.6 = 78 standard deviation = npq = 130 x 0.6 x 0.4 = 31.2
P(X<=90) = ? X~N(78,31.2)

applyin continuity correction;
P(X<90.5)
=> P[((X-mean)/standard deviation) < ((90.5 - 78)/rootof31.2)]
now standardise X, ull get
P(Z<2.238)
from the normal distribution table, find the answer....
Ansswer is 0.987 ..

 

[saloom987]

thanks man i really appreciate it