Estimating Population Parameters with Error Margin

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Statistics › Estimating Population Parameters with Error Margin

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1

A park district wants to estimate the population parameter $p$, the proportion of all residents who visited a park in the last month. A random sample of $n=150$ residents found a sample statistic $\hat{p}=0.48$ (48%). Students used simulation/repeated sampling and reported: in 1,000 simulated samples of size 150, about 95% of the simulated sample proportions were within 0.05 of 0.48.

Which interval is a reasonable estimate range for the population parameter $p$? (Give the interval in decimals.)

$0.38$ to $0.58$

$0.475$ to $0.485$

$0.43$ to $0.53$

$0.48$ to $0.53$

Explanation

The idea is using simulation to find a margin of error for the population proportion p of park visitors. By simulating repeated samples of size 150, we get a distribution of proportions around the sample's 0.48. MOE is the distance from the center that includes 95% of simulated proportions, showing sampling error. The report says 95% are within 0.05 of 0.48, so the interval is 0.43 to 0.53. This range is a reasonable estimate for p. Avoid confusing decimal MOE (0.05) with percent (5%); the question wants decimals. To use this strategy, locate the 95% middle spread in simulations and halve it if needed for MOE.

2

A store wants to estimate the population parameter $p$, the proportion of all customers who use self-checkout. A random sample of 500 customers found 310 used self-checkout, so the sample statistic is $\hat p = 310/500 = 0.62$ (62%). Students ran a simulation of 1,000 repeated random samples of size 500 and found that about 95% of simulated sample proportions were between 0.58 and 0.66.

What margin of error is supported by the simulation for estimating the population parameter $p$? (Express your answer as a percent.)

$\pm 0.04%$

$\pm 8%$

$\pm 62%$

$\pm 4%$

Explanation

Simulation helps estimate the margin of error for the proportion p using self-checkout. Repeated samples produce a distribution of proportions, revealing variability. MOE is the typical distance capturing 95% around the center. The 95% from 0.58 to 0.66 (58% to 66%) gives a width of 8%, so MOE is ±4%. This is a reasonable error margin for estimating p at 62%. Common error: mistaking full width for MOE or using decimals when percents are asked. Always locate the middle 95% in simulations and halve its spread for the MOE in percent form if required.

3

A park service wants to estimate the population parameter $\mu$, the mean number of minutes visitors spend on a particular trail. A random sample of 25 visitors had a sample mean (sample statistic) of $\bar x = 52$ minutes. A simulation of 1,000 repeated random samples of size 25 produced a distribution of simulated sample means whose middle 95% was from 46 to 58 minutes.

What margin of error is supported by the simulation for estimating the population parameter $\mu$?

$\pm 52$ minutes

$\pm 6$ minutes

$\pm 0.06$ minutes

$\pm 12$ minutes

Explanation

Simulation aids in estimating the margin of error for the mean μ of trail time in minutes. Repeated random samples yield a distribution of means, demonstrating sampling fluctuation. The MOE is the offset from the sample mean that covers 95% of simulated means. Here, the middle 95% from 46 to 58 minutes has a width of 12, so MOE is ±6 minutes. This gives a plausible range of 46 to 58 for μ based on the 52-minute sample. A common mix-up is using the full width as MOE instead of half; also, keep it in minutes, not decimals. For other cases, identify the 95% central spread and take half as your simulation-based MOE.

4

A library wants to estimate the population parameter $p$, the proportion of all patrons who prefer e-books over print books. A random sample of 120 patrons found that 45 preferred e-books, so the sample statistic is $\hat p = 45/120 = 0.375$ (37.5%). Students ran a simulation of 2,000 repeated random samples of size 120, and the middle 95% of simulated sample proportions ran from 0.29 to 0.46.

What margin of error is supported by the simulation for estimating the population parameter $p$? (Give the margin of error as a proportion.)

$\pm 8.5$

$\pm 0.085$

$\pm 0.17$

$\pm 0.375$

Explanation

Simulation is key for estimating the margin of error in the proportion p of patrons preferring e-books. Through repeated random samples, we build a distribution of sample proportions to see natural variability. The MOE represents the distance from the center that encloses about 95% of simulated proportions. In this case, the middle 95% from 0.29 to 0.46 gives a full width of 0.17, so the MOE is ±0.085 (half of that). Thus, a plausible range for p is 0.375 ± 0.085, or 0.29 to 0.46. A misconception is treating the MOE as a percent instead of a decimal proportion—here it's 0.085, not 8.5%. Always look for the middle 95% spread in simulations and halve it to get the MOE for reliable estimates.

5

A student council wants to estimate the population parameter $p$, the proportion of all students who support a new lunchtime schedule. A random sample of 80 students found 44 in support, so the sample statistic is $\hat p = 44/80 = 0.55$. Students ran two simulations to compare sample sizes.

  • For samples of size 80, about 95% of simulated $\hat p$ values were between 0.44 and 0.66.
  • For samples of size 320, about 95% of simulated $\hat p$ values were between 0.49 and 0.61.

Which interval is a reasonable estimate range for the population parameter $p$ if the council uses the larger sample size $n=320$?

$0.49$ to $0.61$

$0.55$ to $0.61$

$0.06$ to $0.12$

$0.44$ to $0.66$

Explanation

Using simulation, we estimate the margin of error for the proportion p supporting a new schedule, comparing sample sizes. Repeated samples create distributions of proportions, with larger n reducing variability. MOE is the distance capturing 95% of simulated results around the center. For n=320, 95% fell between 0.49 and 0.61, so that's a reasonable interval for p. This narrower range reflects less uncertainty with bigger samples. Don't confuse full width (0.12) with MOE (±0.06), and remember proportions vs. percents. Look for the middle 95% spread in simulations for your sample size and halve it for MOE.

6

A gym wants to estimate the population parameter $\mu$, the mean number of days per week all members work out. A random sample of 60 members gave a sample mean (sample statistic) of $\bar x = 3.9$ days. Students used simulation with 2,000 repeated random samples of size 60. The results showed that about 95% of simulated sample means were within 0.4 days of 3.9.

Which interval is a reasonable estimate range for the population parameter $\mu$ based on the simulation? (Round endpoints to the nearest tenth.)

$3.86$ to $3.94$

$3.9$ to $4.3$

$3.9 \pm 0.8$

$3.5$ to $4.3$

Explanation

Simulation estimates the margin of error for the mean μ of workout days per week. Repeated samples generate a distribution of means, illustrating variation. MOE is the distance around the sample mean capturing 95% of simulated means, here ±0.4 days. This creates a plausible interval from 3.5 to 4.3 for μ based on 3.9. The range accounts for sampling uncertainty. Avoid confusing full width (0.8) with MOE (half); round as needed but keep decimals accurate. In transfers, find the central 95% spread and divide by two for your MOE from simulation data.

7

A community center wants to estimate the population parameter $p$, the proportion of all local residents who would attend a free weekend class. A random sample of 300 residents found that 147 said “yes,” so the sample statistic is $\hat p = 147/300 = 0.49$ (49%). Students used simulation to model repeated random sampling of size 300. Their summary said: “In 1,000 simulated samples, about 95% of the simulated sample proportions were within 0.06 of 0.49.”

What does the margin of error mean in context?

The simulation guarantees the true population parameter $p$ is between 0.43 and 0.55.

The population parameter $p$ changes by about 0.06 from sample to sample.

If many random samples of 300 residents were taken, the sample statistic $\hat p$ would typically be within about 0.06 of the population parameter $p$.

About 95% of individual residents have a true probability between 0.43 and 0.55 of attending.

Explanation

Simulation estimates the margin of error for the proportion p of residents attending a class. By simulating repeated samples, we get a distribution of sample proportions showing expected variability. The MOE is the distance from the center that includes about 95% of these proportions, like ±0.06 here. The simulation found 95% within 0.06 of 0.49, meaning sample proportions typically fall within 0.06 of the true p. This interprets the MOE as how close our sample statistic likely is to the population parameter in repeated sampling. A misconception is thinking MOE is the full width (0.12) rather than half; also, it's not about individual probabilities but sample statistics. To transfer, find the middle 95% deviation in simulations and use half as MOE for interpretation.

8

A community center wants to estimate the population parameter $p$, the proportion of all families in the community that attend at least one event each month. A random sample of $n=100$ families gave a sample statistic $\hat{p}=0.40$ (40%). Students simulated 1,000 repeated random samples of size 100 and found that the middle 95% of simulated sample proportions ranged from 0.31 to 0.49.

What margin of error is supported by the simulation (in percentage points)?

9 percentage points

0.09 percentage points

40 percentage points

18 percentage points

Explanation

The concept involves simulating to estimate margin of error for the population proportion p of event attendees. Repeated samples of size 100 create a distribution around the sample's 0.40. MOE is half the interval width that holds 95% of simulated proportions, reflecting variability. The middle 95% is 0.31 to 0.49 (31% to 49%), width 18 points, so MOE is 9 percentage points. Thus, p is estimated at 40% ± 9 points. People often forget to convert to percentage points; here it's specified. In general, find the 95% range in the simulation and halve its width for MOE.

9

A city wants to estimate the population parameter $p$, the proportion of all households in the city that recycle weekly. A random sample of $n=200$ households found a sample statistic $\hat{p}=0.62$ (62%). Students used a simulation that repeatedly took 1,000 random samples of size 200 (assuming the true proportion is close to 0.62) and recorded the simulated sample proportions. In the simulation, about 95% of the simulated sample proportions were between 0.55 and 0.69.

Which interval is a reasonable estimate range for the population parameter $p$ based on the simulation?

$0.62 \pm 0.14$ (about 48% to 76%)

$0.62 \pm 0.007$ (about 61.3% to 62.7%)

$0.62 \pm 0.07$ (about 55% to 69%)

$0.55 \pm 0.69$ (about -14% to 124%)

Explanation

We're using simulation to estimate the margin of error for a population proportion p, the true recycling rate in the city. By repeatedly taking random samples of size 200, the simulation creates a distribution of possible sample proportions around the observed 0.62. The margin of error is like half the width of the interval that captures about 95% of these simulated proportions, showing the typical variability. Here, the simulation shows 95% of sample proportions between 0.55 and 0.69, so the full width is 0.14 and the MOE is 0.07. This means a plausible range for p is 0.62 ± 0.07, or about 55% to 69%. A common mix-up is using the full width as the MOE instead of half; remember, MOE is the 'plus or minus' part. To apply this elsewhere, find the middle 95% spread in the simulation and halve it for the MOE.

10

A school wants to estimate the population parameter $p$, the proportion of all students at the school who usually bring a reusable water bottle. A random sample of 200 students found that 118 brought a reusable bottle, so the sample statistic is $\hat p = 118/200 = 0.59$ (59%). To model random sampling variability, students ran a simulation of 1,000 random samples of size 200 from a population where the proportion is unknown, but centered at the observed sample statistic. In the simulation, about 95% of the simulated sample proportions were between 0.53 and 0.65.

Which interval is a reasonable estimate range for the population parameter $p$ based on the simulation?

$0.06$ to $0.12$

$0.53$ to $0.65$

$0.59$ to $0.65$

$0.56$ to $0.62$

Explanation

We're using simulation to estimate a margin of error for the population proportion p of students bringing reusable water bottles. By taking repeated random samples, we create a distribution of sample proportions that shows how much they vary due to random sampling. The margin of error is the typical distance from the center of this distribution that captures about 95% of the simulated results, giving us a sense of sampling variability. From the simulation, 95% of the sample proportions fell between 0.53 and 0.65, so the interval from 0.53 to 0.65 represents a plausible range for the true p. This means the population proportion is likely somewhere in that range, based on the observed sample of 0.59. A common misconception is confusing the full interval width (0.12) with the margin of error, which is actually half that (0.06) on each side. To apply this elsewhere, just find the middle 95% spread in your simulation and halve it for the MOE.

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