The per capita energy consumption level​ (in kilowatt-hours) in a certain country for a recent year can be approximated by a normal​ distribution, as shown in the figure.  ​(a) What consumption level represents the 9th ​percentile? ​(b) What consumption level represents the 19th ​percentile? ​(c) What consumption level represents the third ​quartile? ​(a) The consumption level that represents the 9th percentile is enter your response here ​kilowatt-hours. ​(Round to the nearest integer as​ needed.) ​(b) The consumption level that represents the 19th percentile is enter your response here ​kilowatt-hours. ​(Round to the nearest integer as​ needed.) ​(c) The consumption level that represents the third quartile is enter your response here ​kilowatt-hours. ​(Round to the nearest integer as​ needed.)

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The per capita energy consumption level​ (in kilowatt-hours) in a certain country for a recent year can be approximated by a normal​ distribution, as shown in the figure. 
​(a) What consumption level represents the 9th ​percentile?
​(b) What consumption level represents the 19th ​percentile?
​(c) What consumption level represents the third ​quartile?

​(a) The consumption level that represents the
9th
percentile is
enter your response here
​kilowatt-hours.
​(Round to the nearest integer as​ needed.)

​(b) The consumption level that represents the
19th
percentile is
enter your response here
​kilowatt-hours.
​(Round to the nearest integer as​ needed.)

​(c) The consumption level that represents the
third
quartile is
enter your response here
​kilowatt-hours.
​(Round to the nearest integer as​ needed.)

### Normal Distribution of Kilowatt-Hours

The graph above represents a normal distribution of kilowatt-hours (kWh) used. Specifically, this distribution is centered around the mean \( \mu = 2321 \) kWh and has a standard deviation \( \sigma = 570.9 \) kWh.

- **Horizontal Axis (x-axis):** The x-axis represents the kilowatt-hours used, ranging from 321 kWh to 4321 kWh.
    - Major ticks on the x-axis: 321 kWh, 2321 kWh, and 4321 kWh.
- **Vertical Axis (y-axis):** The y-axis represents the frequency or probability density of the kilowatt-hour usage.

**Mean ( \( \mu \) ):**
- The mean value, \( \mu \), is indicated at 2321 kWh. This is the peak of the bell-shaped curve, signifying the average kilowatt-hour usage.

**Standard Deviation ( \( \sigma \) ):**
- The standard deviation, \( \sigma \), is 570.9 kWh. This measurement provides insight into the dispersion or spread of the usage data around the mean. Smaller standard deviations indicate that the data points are closer to the mean, while larger standard deviations indicate that the data points are spread out over a larger range of values.

The bell curve illustrates that most of the kilowatt-hour usages are clustered around the mean (2321 kWh), with fewer occurrences as we move away from the mean. In a normal distribution, about 68% of the data falls within one standard deviation of the mean, about 95% within two standard deviations, and nearly all (99.7%) within three standard deviations.

This graph is an essential tool for understanding the variability and distribution of electricity consumption, useful for energy management, and forecasting usage patterns.
Transcribed Image Text:### Normal Distribution of Kilowatt-Hours The graph above represents a normal distribution of kilowatt-hours (kWh) used. Specifically, this distribution is centered around the mean \( \mu = 2321 \) kWh and has a standard deviation \( \sigma = 570.9 \) kWh. - **Horizontal Axis (x-axis):** The x-axis represents the kilowatt-hours used, ranging from 321 kWh to 4321 kWh. - Major ticks on the x-axis: 321 kWh, 2321 kWh, and 4321 kWh. - **Vertical Axis (y-axis):** The y-axis represents the frequency or probability density of the kilowatt-hour usage. **Mean ( \( \mu \) ):** - The mean value, \( \mu \), is indicated at 2321 kWh. This is the peak of the bell-shaped curve, signifying the average kilowatt-hour usage. **Standard Deviation ( \( \sigma \) ):** - The standard deviation, \( \sigma \), is 570.9 kWh. This measurement provides insight into the dispersion or spread of the usage data around the mean. Smaller standard deviations indicate that the data points are closer to the mean, while larger standard deviations indicate that the data points are spread out over a larger range of values. The bell curve illustrates that most of the kilowatt-hour usages are clustered around the mean (2321 kWh), with fewer occurrences as we move away from the mean. In a normal distribution, about 68% of the data falls within one standard deviation of the mean, about 95% within two standard deviations, and nearly all (99.7%) within three standard deviations. This graph is an essential tool for understanding the variability and distribution of electricity consumption, useful for energy management, and forecasting usage patterns.
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