First, we need to calculate the mean (μ) and standard deviation (σ) of the number of chocolate chips in the 18-ounce bags.
Given data:
\[ 1085, 1155, 1218, 1268, 1345, 1098, 1144, 1200, 1268, 1356, 1124, 1189, 1241, 1296, 1399, 1127, 1195, 1244, 1299, 1432, 1140, 1211, 1254, 1328, 1443 \]
Calculate the mean (μ):
\[ \mu = \frac{\sum X}{N} = \frac{1085 + 1155 + 1218 + 1268 + 1345 + 1098 + 1144 + 1200 + 1268 + 1356 + 1124 + 1189 + 1241 + 1296 + 1399 + 1127 + 1195 + 1244 + 1299 + 1432 + 1140 + 1211 + 1254 + 1328 + 1443}{25} \]
\[ \mu = \frac{30915}{25} = 1236.6 \]
Calculate the standard deviation (σ):
\[ \sigma = \sqrt{\frac{\sum (X - \mu)^2}{N}} \]
\[ \sigma = \sqrt{\frac{(1085-1236.6)^2 + (1155-1236.6)^2 + \ldots + (1443-1236.6)^2}{25}} \]
\[ \sigma \approx 112.6 \]
To find the probability that an 18-ounce bag contains at least 1000 chips, we need to calculate the Z-score for 1000 chips.
\[ Z = \frac{X - \mu}{\sigma} \]
\[ Z = \frac{1000 - 1236.6}{112.6} \]
\[ Z \approx -2.10 \]
Using the Z-score table, find the probability corresponding to \( Z = -2.10 \).
The Z-score table gives the probability to the left of the Z-score:
\[ P(Z < -2.10) \approx 0.0179 \]
Since we need the probability of at least 1000 chips:
\[ P(X \geq 1000) = 1 - P(Z < -2.10) \]
\[ P(X \geq 1000) = 1 - 0.0179 \]
\[ P(X \geq 1000) \approx 0.9821 \]
The probability that an 18-ounce bag of chips contains at least 1000 chips is approximately 0.982.