Peter R. answered 03/14/22
Experienced Instructor in Prealgebra, Algebra I and II, SAT/ACT Math.
Total peas: 433 green + 154 yellow = 587. Proportion yellow 154/587 = 0.26235 or ≈26.2%. This is your point estimate for the population proportion of yellow peas. p "hat" is 0.262; q "hat" is 1 - 0.262 = 0.738 . np"hat" is (587)(0.262) = 154; nq"hat" is (587)(0.738) = 433, so both results are ≥ 5 and the sample can be approximated by a normal distribution. For 90% confidence, zc = 1.645.
The margin of error E is calculated by 1.645 x sqrt[(0.262)(0.738)/587)] = 0.030
The confidence limits are the point estimate ± the margin of error. 0.262 + 0.030 = 0.292 or 29.2%;
0.262 - 0.030 = 0.232, or 23.2%. You can say with 90% confidence that the proportion of yellow peas is between 23.2% and 29.2%, so the 25% estimate falls within the 90% confidence limits.