Grade 11 · Math · Algebra 2

11th grade Confidence intervals from a sample, for averages and for percents worksheet

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Confidence intervals from a sample, for averages and for percents

Grade 11 Math Worksheet

NameDate

Circle the best answer, or write your answer on the line.

Ari's random sample of 100 bus rides has an SD of 15 minutes. Using the 95% multiplier 1.96, what is the margin of error?
Bo's random sample of 64 backpacks has an SD of 20 ounces (one holds a whole library). Using the 95% multiplier 1.96, what is the margin of error?
Esme's random sample of 49 sunflowers has an SD of 14 centimeters. Using the 95% multiplier 1.96, what is the margin of error?
4.
Kira's sample of 64 backpacks has mean 120 ounces and SD 20. What is the 95% interval?
- 115.1 to 124.9 ounces
- 100 to 140 ounces
- 117.5 to 122.5 ounces
5.
Luz's interval is 33.04 to 36.96 minutes. What was the sample mean?
- 3.92 minutes
- 35 minutes
- 1.96 minutes
6.
Milo surveys 400 people instead of 100. What happens to the interval?
- It gets wider
- It gets narrower
- It stays the same
7.
Pia wants half the margin of error. How many times bigger must the sample be?
- 4 times
- 2 times
- 8 times
8.
Ren estimates the average minutes students spend on homework. Which standard error fits?
- p ÷ n
- √(p(1 − p) ÷ n)
- s ÷ √n
9.
Tala estimates the percent of students who walk to school. Which standard error fits?
- √(p(1 − p) ÷ n)
- s ÷ n
- s ÷ √n
10.
In Zee's random sample, 90 of 300 students have a pet. What is the sample proportion p?
- 0.30
- 3.33
- 0.90

Confidence intervals from a sample, for averages and for percents. Every version has 10 questions, and the answer key prints on the second page.

I can find the standard error of a mean, s ÷ √n, and of a proportion, √(p(1 − p) ÷ n).
I can read the multiplier from a table (1.645, 1.96, 2.576) and build an interval from sample data.
I can say how sample size and confidence level change the width.
I can say what an interval does and doesn't claim, and use it to judge a claim.

Standard: S-IC.B.4

confidence interval: A range of believable values for the true mean or percent

standard error: How much a sample result tends to vary

margin of error: Multiplier × standard error, added and subtracted

multiplier z*: A table number for the confidence level

sample proportion p: The share of the sample with the trait

Your child divided by n. The standard error of a mean divides the SD by the square root of n.

Your child found the standard error but didn't multiply by the table's 1.96. The margin of error is multiplier × standard error.

Your child used the rough margin 1 ÷ √n. With the sample's own percent, the margin is 1.96 × √(p(1 − p) ÷ n).

What is the most common mistake with confidence intervals from a sample, for averages and for percents?

Your child divided by n. The standard error of a mean divides the SD by the square root of n.

Are these 11th grade math worksheets free to print?

Yes. All 6 printable versions at each level are free to print, with the answer key, and no account is needed.

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