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Water Quality: The Evidence Desk

Use water-quality samples to estimate population results, compare repeated samples, and evaluate the strength of lab conclusions.

Grade 7MathInteractive · Printable

Aligned to7.SP.A.2

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What’s included

Single worksheet
Auto-graded online
1 Common Core standard
Printable answer key
13 questions
Classroom-ready

Details

Format: Interactive · Printable
Grade: Grade 7
Subject: Math
Question types: Fill in the blank, Multiple choice, Sorting, Short answer

About this worksheet

What students practice

Students use random-sample proportions and means to estimate population results.
Students compare estimates from repeated random samples and describe their variation.
Students distinguish additional random observations from repeated measurements of the same observations.

How to use

Have students show their sample-to-population calculations. Discuss how repeated random samples reveal uncertainty without measuring every bottle.

Curriculum

Common Core standard covered

7.SP.A.2

Use data from a random sample to make inferences about a population, and compare several samples to see how estimates vary.

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Water Quality: The Evidence Desk

Use random samples to estimate water-quality results and compare their variation.

Review the Nitrate Results

A community science lab stores 840 water bottles collected during one week. Each bottle represents one collection. The lab randomly selects 60 different bottles, giving every bottle an equal chance of selection. Use the sample to estimate results for all 840 bottles. Treat the cutoffs below as lab review rules, not drinking-water safety standards.

Nitrate Results: Random Sample of 60 Bottles
Nitrate (mg/L)	Number of bottles
Less than 3	15
3 to less than 6	27
6 or greater	18

The lab files bottles with nitrate below 6 mg/L in its routine-review group. Which estimate should it use for the number of routine-review bottles among all 840?