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Question 5 ,
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HW Score: 
73.89%,
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Part 3 of 4

(x) Points: 0.5 of 1
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A simple random sample of size 
n=14 is obtained from a population with 
mu=69 and 
sigma=16.
(a) What must be true regarding the distribution of the population in order to use the normal model to compute probabilities involving the sample mean? Assuming that this condition is true, describe the sampling distribution of 
bar(x).
(b) Assuming the normal model can be used, determine 
P( bar(x) < 73.4).
(c) Assuming the normal model can be used, determine 
P( bar(x) >= 70.7).
(a) What must be true regarding the distribution of the population?
A. Since the sample size is large enough, the population distribution doe need to be normal.
B. The sampling distribution must be assumed to be normal.
C. The population must be normally distributed.
D. The population must be normally distributed and the sample size must be large.
Assuming the normal model can be used, describe the sampling distribution 
bar(x). Choose the correct answer below.

\begin{tabular}{|c|c|c|c|}\newline\hline Question 55 , & ר & HW Score: 73.89% 73.89 \% , & \{్ర \\\newline\hline Part 33 of 44 & & (x) Points: 00.55 of 11 & Save \\\newline\hline\newline\end{tabular}\newlineA simple random sample of size n=14 n=14 is obtained from a population with μ=69 \mu=69 and σ=16 \sigma=16 .\newline(a) What must be true regarding the distribution of the population in order to use the normal model to compute probabilities involving the sample mean? Assuming that this condition is true, describe the sampling distribution of xˉ \bar{x} .\newline(b) Assuming the normal model can be used, determine P(xˉ<73.4) \mathrm{P}(\bar{x}<73.4) .\newline(c) Assuming the normal model can be used, determine P(xˉ70.7) P(\bar{x} \geq 70.7) .\newline(a) What must be true regarding the distribution of the population?\newlineA. Since the sample size is large enough, the population distribution doe need to be normal.\newlineB. The sampling distribution must be assumed to be normal.\newlineC. The population must be normally distributed.\newlineD. The population must be normally distributed and the sample size must be large.\newlineAssuming the normal model can be used, describe the sampling distribution xˉ \bar{x} . Choose the correct answer below.

Full solution

Q. \begin{tabular}{|c|c|c|c|}\newline\hline Question 55 , & ר & HW Score: 73.89% 73.89 \% , & \{్ర \\\newline\hline Part 33 of 44 & & (x) Points: 00.55 of 11 & Save \\\newline\hline\newline\end{tabular}\newlineA simple random sample of size n=14 n=14 is obtained from a population with μ=69 \mu=69 and σ=16 \sigma=16 .\newline(a) What must be true regarding the distribution of the population in order to use the normal model to compute probabilities involving the sample mean? Assuming that this condition is true, describe the sampling distribution of xˉ \bar{x} .\newline(b) Assuming the normal model can be used, determine P(xˉ<73.4) \mathrm{P}(\bar{x}<73.4) .\newline(c) Assuming the normal model can be used, determine P(xˉ70.7) P(\bar{x} \geq 70.7) .\newline(a) What must be true regarding the distribution of the population?\newlineA. Since the sample size is large enough, the population distribution doe need to be normal.\newlineB. The sampling distribution must be assumed to be normal.\newlineC. The population must be normally distributed.\newlineD. The population must be normally distributed and the sample size must be large.\newlineAssuming the normal model can be used, describe the sampling distribution xˉ \bar{x} . Choose the correct answer below.
  1. Question Prompt: Question Prompt: Determine the conditions required for using the normal model for the sample mean and calculate probabilities for given conditions using the normal distribution.
  2. Step 11: Step 11: For the normal model to be applicable, the population from which the sample is drawn must be normally distributed. This is because the Central Limit Theorem, which allows the use of the normal model for the sample mean, requires either a normal population distribution or a sufficiently large sample size (usually n30n \geq 30) to approximate normality. Here, since n=14n=14, which is not large, the population must be normally distributed. Correct answer: C.
  3. Step 22: Step 22: Assuming the population is normally distributed, the sampling distribution of the sample mean xˉ \bar{x} will also be normally distributed. The mean of xˉ \bar{x} is equal to the population mean μ \mu , and the standard deviation of xˉ \bar{x} (standard error) is σ/n \sigma / \sqrt{n} . Calculation: σ/14=16/144.28 \sigma / \sqrt{14} = 16 / \sqrt{14} \approx 4.28 .
  4. Step 33: Step 33: To find P(xˉ<73.4) P(\bar{x} < 73.4) , convert xˉ \bar{x} to a standard normal variable Z Z . Calculation: Z=(xˉμ)/(σ/n)=(73.469)/4.281.03 Z = (\bar{x} - \mu) / (\sigma / \sqrt{n}) = (73.4 - 69) / 4.28 \approx 1.03 . Use the Z-table to find P(Z<1.03)0.8485 P(Z < 1.03) \approx 0.8485 .
  5. Step 44: Step 44: To find P(xˉ70.7) P(\bar{x} \geq 70.7) , first calculate Z Z for 7070.77. Calculation: Z=(70.769)/4.280.40 Z = (70.7 - 69) / 4.28 \approx 0.40 . Use the Z-table to find P(Z<0.40)0.6554 P(Z < 0.40) \approx 0.6554 . Since we need P(Z0.40) P(Z \geq 0.40) , it is 10.6554=0.3446 1 - 0.6554 = 0.3446 .

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