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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 4 decimal places, evaluate \( P(X<7.97) \) 0.7734 0.4533 0.5467 0.2266 None of the above. ** Note: Do not round any z-score.

Ask by Adkins Barker. in the United States
Mar 09,2025

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Answer

\( P(X < 7.97) = 0.2266 \)

Solution

1. The length \( X \) follows a normal distribution with mean \(\mu = 8\) cm and standard deviation \(\sigma = 0.04\) cm. 2. To evaluate \( P(X < 7.97) \), first compute the corresponding z-score: \[ z = \frac{X - \mu}{\sigma} = \frac{7.97 - 8}{0.04} = \frac{-0.03}{0.04} = -0.75. \] 3. Now, \( P(X < 7.97) = P(Z < -0.75) \). 4. Using the symmetry of the standard normal distribution: \[ P(Z < -0.75) = 1 - P(Z < 0.75). \] Typically, \( P(Z < 0.75) \) is approximately \( 0.7734 \). Therefore, \[ P(Z < -0.75) = 1 - 0.7734 = 0.2266. \] 5. Thus, the probability is accurate to four decimal places: \( 0.2266 \).

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To evaluate \( P(X < 7.97) \), we first need to calculate the z-score using the formula: \[ z = \frac{X - \mu}{\sigma} \] Where: - \( X = 7.97 \) - \( \mu = 8 \) - \( \sigma = 0.04 \) Plugging in the values: \[ z = \frac{7.97 - 8}{0.04} = \frac{-0.03}{0.04} = -0.75 \] Next, we look up the z-score of -0.75 in the standard normal distribution table, or use a calculator, to find \( P(Z < -0.75) \). This gives us approximately 0.2266. So, the answer is **0.2266**. Now for some interesting insights, did you know the concept of the normal distribution was significantly advanced by Carl Friedrich Gauss in the 18th century? His work with the distribution laid the foundation for what we now recognize as the standard normal curve that is ubiquitous in statistics today! Additionally, understanding how to utilize z-scores is a key problem-solving tip in statistics. Many students make the mistake of not knowing how to properly find their corresponding probabilities or confuse the direction of the inequalities when looking up values. Always remember: if you’re looking for \( P(Z < z) \), stick to the cumulative distribution table for your reference!

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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