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The length of similar components produced by a company are approximated by a normal distribution model with a mean of 8 cm and a standard deviation of 0.04 cm . Let the random variable X represent the length of one component chosen at random. Accurate to 2 decimal places, the \( 79^{\text {th }} \) percentile has z -score 0.81 0.83 0.79 0.82 0.8

Ask by Coles Vaughan. in the United States
Mar 09,2025

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Answer

The z-score for the 79th percentile is 0.81.

Solution

1. We need to find the z-score, \( z \), corresponding to the \( 79^{\text{th}} \) percentile. This means we want to find \( z \) such that \[ P(Z \leq z) = 0.79, \] where \( Z \) is a standard normal random variable. 2. Using a standard normal table or an appropriate calculator (or software) to find the percentile, we determine that the z-score that satisfies \[ \Phi(z) = 0.79 \] is approximately \[ z \approx 0.81. \] 3. Therefore, the z-score corresponding to the \( 79^{\text{th}} \) percentile is \( \boxed{0.81} \).

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The Deep Dive

To find the 79th percentile of a normally distributed variable, you can use the z-score formula: \[ X = \mu + z \cdot \sigma \] In this case, the mean \( \mu \) is 8 cm and the standard deviation \( \sigma \) is 0.04 cm. Using the given z-score of 0.81, we calculate: \[ X = 8 + 0.81 \cdot 0.04 \approx 8.0324 \] So, rounding to two decimal places, the 79th percentile is approximately 8.03 cm! To double-check your z-scores: most statistical tables or calculators show that the z-score for the 79th percentile is indeed around 0.81, but using a z-score of around 0.80 is another close approximation! Just remember, the more precise your calculations and values, the more accurate your results will be!

Related Questions

Question 12(Mulliple Choice Warth 5 points) \[ (04.06 \mathrm{HC}) \] A researcher wants to test the claim that the proportion of juniors who watch television regularly is greater than the proportion of seniors who watch television regularly She finds that 56 of 70 randomly selected juniors and 47 of 85 randomly selected seniors report watching television regularly. Construct \( 95 \% \) confidence intervals for each population proportion. Which of the statemente gives the correct outcome of the research or's tert of the dalim? The \( 95 \% \) confidence interval for juniors is (706, 894), and the \( 95 \% \) confidence interval for seniors is ( 447,659 ). Since the intervals overlap, there is not enough evidence to say the proportion of juniors who watch television regularly may be higher than that of seniors. The \( 95 \% \) confidence interval for juniors is (721, 879), and the \( 95 \% \) confidence interval for seniors is (464, 642). Since the interval for juniors is higher than the interval for seniors, there is evidence to say the proportion of juniors who watch television regularly may be higher than that of seniors. The \( 95 \% \) confidence interval for juniors is ( 706,894 ), and the \( 95 \% \) confidence interval for seniors is ( 447,659 ). Since the interval for juniors is higher than the interval for seniors, there is evidence to say the proportion of juniors who watch television regularly may be higher than that of seniors. The \( 95 \% \) confidence interval for juniors is ( \( 721, .879 \) ), and the \( 95 \% \) confidence interval for seniors is (464, 642). Since the intervals overlap, there is not enough evidence to say the proportion of juniors who watch television regularly may be higher than that of seniors.

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