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Find the \( z \)-score corresponding to the given area. Round to two decimals, if necessary, The area to the left of \( z \) is \( 60 \% \). \( z=\square \) The area to the right of \( z \) is \( 10 \% \). The area between \( -z \) and \( z \) is \( 97 \% \). \( z=\square \)

Ask by Lindsey Williams. in the United States
Jan 21,2025

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Answer

\( z = 0.25 \) \( z = 1.28 \) \( z = 2.05 \)

Solution

Alright, I need to find the \( z \)-scores corresponding to the given areas. Let's tackle each part one by one. **First Problem:** - **Given:** The area to the left of \( z \) is \( 60\% \). - **To Find:** The \( z \)-score \( z \). Since the area to the left of \( z \) is \( 60\% \), this means that \( z \) is the 60th percentile in the standard normal distribution. To find the exact \( z \)-score, I'll use the standard normal distribution table or a calculator that provides the inverse cumulative distribution function. Looking up \( 60\% \) in the standard normal distribution table: - The table typically provides the cumulative area from the left up to a certain \( z \)-value. - For \( 60\% \), the corresponding \( z \)-score is approximately \( 0.25 \). So, \( z \approx 0.25 \). **Second Problem:** - **Given:** The area to the right of \( z \) is \( 10\% \). - **To Find:** The \( z \)-score \( z \). The area to the right of \( z \) being \( 10\% \) implies that the area to the left of \( z \) is \( 90\% \) (since the total area under the curve is \( 100\% \)). Using the standard normal distribution table: - \( 90\% \) corresponds to a \( z \)-score of approximately \( 1.28 \). Therefore, \( z \approx 1.28 \). **Third Problem:** - **Given:** The area between \( -z \) and \( z \) is \( 97\% \). - **To Find:** The \( z \)-score \( z \). The area between \( -z \) and \( z \) represents the central \( 97\% \) of the distribution. This means that \( 97\% \) of the data lies within \( z \) standard deviations from the mean. To find \( z \), I'll use the property that the area between \( -z \) and \( z \) is \( 2 \times \text{Area from } 0 \text{ to } z \). So, \( 2 \times \text{Area from } 0 \text{ to } z = 97\% \). This simplifies to: \[ \text{Area from } 0 \text{ to } z = 48.5\% \] Looking up \( 48.5\% \) in the standard normal distribution table: - The corresponding \( z \)-score is approximately \( 2.05 \). Therefore, \( z \approx 2.05 \). **Summary of Findings:** 1. For the area to the left of \( z \) being \( 60\% \), \( z \approx 0.25 \). 2. For the area to the right of \( z \) being \( 10\% \), \( z \approx 1.28 \). 3. For the area between \( -z \) and \( z \) being \( 97\% \), \( z \approx 2.05 \).

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The Deep Dive

To find the \( z \)-score corresponding to the area to the left of \( z \) being \( 60\% \), you can use standard normal distribution tables or a calculator. The area of \( 60\% \) implies that \( z \) is the value where \( 60\% \) of the data lies to the left. Looking it up, the \( z \) corresponding to \( 0.60 \) is approximately \( 0.25 \). Next, for the area to the right of \( z \) being \( 10\% \), that leaves \( 90\% \) to the left. Therefore, you are looking for where \( 90\% \) of the distribution falls to the left. From the standard normal distribution table, the \( z \) corresponding to \( 0.90 \) is approximately \( 1.28 \). Lastly, for the area between \( -z \) and \( z \) being \( 97\% \), the area in the tails combined is \( 3\% \) (or \( 1.5\% \) in each tail). Therefore, you want to find the \( z \) value where \( 1.5\% \) is to the left. Look it up, and you find the corresponding \( z \) around \( 2.17 \). So, the answers are: 1. \( z \approx 0.25 \) 2. \( z \approx 1.28 \) 3. \( z \approx 2.17 \)

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