Name: Date:
Student Exploration: Estimating Population Size
Directions: Follow the instructions to go through the simulation. Respond to the questions and
prompts in the orange boxes.
Vocabulary: percent error, population, sample
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
1. A jar contains 100 marbles total. Some are black. If you pull 4 marbles out and 1 is black, how many out of
the 100 marbles would you guess are black? Explain.
Maybe 25 percent of the marbles would be black because that would mean that only one of
four black marbles would come out which is an extremely low number
2. A different jar has 100 black marbles. (The total number of marbles is unknown.) If you pull 4 marbles out
and 1 is black, what is your guess for the total number of marbles? Explain.
I am guessing that there is a total of 500 marbles because I think that there would be 100
black and the rest would be whatever color it would be
Gizmo Warm-up
In the Estimating Population Size Gizmo, you will estimate the total number of fish
in a pond. You will do this by tagging and releasing a certain number of fish, and
then “recapturing” some.
To change the number of fish to tag or catch, drag the slider, or click on the
number in the text field next to a slider, type a new value, and hit Enter.
1. Suppose a scientist tags 100 fish, and releases them. (Set the Tagged fish in pond to 100 to show this.)
Later, a fisherman catches 50 fish from the same pond. (Set Fish to catch to 50 to show this.) The
fisherman’s catch is a sample of all fish in the pond.
A. Click Catch and check. Look at the Results table. How The fisherman caught 50 fish and out of
many tagged fish did the fisherman catch? those fish 26 of them were tagged
B. What percent of the fish in his sample were tagged? 26 percent of the fish were tagged but
each time it re-do it the numbers change
2. At the bottom of the Gizmo, select Show total fish in pond. How many fish are in this pond?
There are 184 fish in this pond
Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved
, This number is the population of fish in this pond.
Activity A: Get the Gizmo ready:
Capture/recapture ● Be sure Show total fish in pond is selected on
method the POND tab.
The “capture/recapture” method lets you estimate the size of a population. To apply this to a fish pond, first
catch and tag some fish. (This is the “capture” part.) Then release the tagged fish into the pond and wait. Later,
catch a second group of fish. (This is the “recapture” part.) Count the tagged fish in the second group and use
a proportion to estimate the pond’s fish population.
1. Set the Tagged fish in pond to 50. Click New pond.
A. How many fish are in this pond?
there are 306 fish in the pond
B. If you catch one fish out of this pond, what is the probability that your fish is tagged?
100 Decimal (to nearest hundredth): 2
Fraction:
50
C. Suppose you catch 100 fish out of this pond. About how many of these fish would you expect to be
tagged? Explain.
I think that 25 or maybe a little less of half would be tagged because there are
overall so many tagged and not tagged fish that i believe it is harder to find the
tagged ones then the not tagged ones
D. Set the Fish to catch to 100. Click Catch and check. How does the number of tagged fish shown
in the Gizmo table compare to your estimate above?
My estimate was right the catched fish with no tags was 100 which I suspected and
the tagged fish caught was only 27
E. If you don’t know how many fish are in the pond, you can use the results from the catch to write a
proportion to estimate the fish population. Fill in the blanks below with words to write this proportion.
tagged fish caught tagged fish in pond
=
total fish caught total fish in pond (estimate)
Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved
Student Exploration: Estimating Population Size
Directions: Follow the instructions to go through the simulation. Respond to the questions and
prompts in the orange boxes.
Vocabulary: percent error, population, sample
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
1. A jar contains 100 marbles total. Some are black. If you pull 4 marbles out and 1 is black, how many out of
the 100 marbles would you guess are black? Explain.
Maybe 25 percent of the marbles would be black because that would mean that only one of
four black marbles would come out which is an extremely low number
2. A different jar has 100 black marbles. (The total number of marbles is unknown.) If you pull 4 marbles out
and 1 is black, what is your guess for the total number of marbles? Explain.
I am guessing that there is a total of 500 marbles because I think that there would be 100
black and the rest would be whatever color it would be
Gizmo Warm-up
In the Estimating Population Size Gizmo, you will estimate the total number of fish
in a pond. You will do this by tagging and releasing a certain number of fish, and
then “recapturing” some.
To change the number of fish to tag or catch, drag the slider, or click on the
number in the text field next to a slider, type a new value, and hit Enter.
1. Suppose a scientist tags 100 fish, and releases them. (Set the Tagged fish in pond to 100 to show this.)
Later, a fisherman catches 50 fish from the same pond. (Set Fish to catch to 50 to show this.) The
fisherman’s catch is a sample of all fish in the pond.
A. Click Catch and check. Look at the Results table. How The fisherman caught 50 fish and out of
many tagged fish did the fisherman catch? those fish 26 of them were tagged
B. What percent of the fish in his sample were tagged? 26 percent of the fish were tagged but
each time it re-do it the numbers change
2. At the bottom of the Gizmo, select Show total fish in pond. How many fish are in this pond?
There are 184 fish in this pond
Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved
, This number is the population of fish in this pond.
Activity A: Get the Gizmo ready:
Capture/recapture ● Be sure Show total fish in pond is selected on
method the POND tab.
The “capture/recapture” method lets you estimate the size of a population. To apply this to a fish pond, first
catch and tag some fish. (This is the “capture” part.) Then release the tagged fish into the pond and wait. Later,
catch a second group of fish. (This is the “recapture” part.) Count the tagged fish in the second group and use
a proportion to estimate the pond’s fish population.
1. Set the Tagged fish in pond to 50. Click New pond.
A. How many fish are in this pond?
there are 306 fish in the pond
B. If you catch one fish out of this pond, what is the probability that your fish is tagged?
100 Decimal (to nearest hundredth): 2
Fraction:
50
C. Suppose you catch 100 fish out of this pond. About how many of these fish would you expect to be
tagged? Explain.
I think that 25 or maybe a little less of half would be tagged because there are
overall so many tagged and not tagged fish that i believe it is harder to find the
tagged ones then the not tagged ones
D. Set the Fish to catch to 100. Click Catch and check. How does the number of tagged fish shown
in the Gizmo table compare to your estimate above?
My estimate was right the catched fish with no tags was 100 which I suspected and
the tagged fish caught was only 27
E. If you don’t know how many fish are in the pond, you can use the results from the catch to write a
proportion to estimate the fish population. Fill in the blanks below with words to write this proportion.
tagged fish caught tagged fish in pond
=
total fish caught total fish in pond (estimate)
Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved
