Answer:
23%<x<43%
Step-by-step explanation:
The formula for calculating confidence interval is expressed;
Confidence Interval = p ± z√p(1-p)/n
n is the sample size
z is the z score at 98% confidence interval
n is the sample size = 120
z = 2.33
If in a randomly chosen handful of 120 beans 40 were black, then;
p = 40/120
p = 4/12
p = 0.33
CI = 0.33± 2.33√0.33(1-0.33)/120
CI = 0.33± [2.33√0.33(0.67)/120]
CI = 0.33± [2.33√0.2211/120]
CI = 0.33± [2.33(0.04292)]
CI = 0.33±0.100014
CI = (0.33-0.100014, 0.33+0.100014)
CI = (0.229, 0.430014)
CI = (22.9, 43.0014)
Hence 98% confidence interval for the proportion of black beans in the jar is 23%<x<43%.
