In: Statistics and Probability
Three-circle, red-on-white is one distinctive pattern painted on ceramic vessels of the Anasazi period found at an archaeological site. At one excavation, a sample of 181 potsherds indicated that 80 were of the three-circle, red-on-white pattern.
(a) Find a point estimate p̂ for the proportion of all
ceramic potsherds at this site that are of the three-circle,
red-on-white pattern. (Round your answer to four decimal
places.)
(b) Compute a 95% confidence interval for the population proportion
p of all ceramic potsherds with this distinctive pattern
found at the site. (Round your answers to three decimal
places.)
lower limit | |
upper limit |
Solution :
Given that,
n = 181
x = 80
Point estimate = sample proportion = = x / n =80/181=0.4420
1 - = 1- 0.4420 =0.5580
At 95% confidence level the z is ,
= 1 - 95% = 1 - 0.95 = 0.05
/ 2 = 0.05 / 2 = 0.025
Z/2 = Z0.025 = 1.96 ( Using z table )
Margin of error = E = Z/2 * ((( * (1 - )) / n)
= 1.96 (((0.4420*0.5580) /181 )
E = 0.072
A 95% confidence interval for population proportion p is ,
- E < p < + E
0.4420-0.072 < p <0.4420+ 0.072
0.370< p <0.514
The 95% confidence interval for the population proportion p is : lower limit=0.370,upper limit=0.514