Math 7: Random Sampling Activity

Random Sampling http://www.biologycorner.com/worksheets/random_sampling.html

Name ______Pd. ______Date ______Math 7: Random Sampling Activity Name: ______Random Sampling Scientists cannot possibly count every organism in a population. One way to estimate the size of a populationScientists ca isnn otot pcollectossibly codataunt byeve takingry organ randomism in a p samples.opulation. O Inne this way activity,to estima youte th ewill size look of a atpo phowulati odatan is t oobtained collect da ta fromby ta kirandomng rando samplingm samples. compare In this acti viwithty, yo datau wil l obtainedlook at ho wby da anta o actualbtained count.from random sampling compare with data obtained by an actual count. Procedure: Procedure:

1.1. TearTear a a sh sheeteet of pofa ppaperer into 2into0 sl i20ps, eslips,ach a peachproxi mapproximatelyately 4cm x 4 cm 4cm. x 4 cm.

2.2. NumberNumber 1 010 of ofth ethe slip slipss from from 1 to 1 10 aton d10 pu andt them put in athem smal lin co ant asmalliner. bag. Label the remaining 10 slips from A through3. Label tJhe and rem aputinin themg 10 sl iinps afr osecondm A thro bag.ugh J and put them in a second container.

The grid shown below represents a meadow measuring 10 m on each side. Each grid segment is 1m x 1m. Each black circle represents one sunflower plant.

3.4. RandomlyRandomly re removemove one one slip fsliprom efromach coeachntain bag.er. W rWriteite dow downn the n uthemb enumber-letterr-letter combina tcombinationion and find th eand grid findsegm theent gridthat segmentmatches t hthate co mmatchesbination. Ctheou ncombination.t the number of Countsunflow theer p lanumbernts in tha oft g sunflowerrid segment .plants Record in th ithats nu mgridber osegment.n the data tRecordable. thisRetu numberrn each sl onip t othe its adatappro ptable.riate co Returnntainer. each slip to its appropriate container.

5. Repeat step 5 until you have data for 10 different grid segments (and the table is filled out). These 10 grid segments 4. Repeat step 5 until you have data for 10 different grid segments (and the table is filled out). These 10 grid represent a sample. Gathering data from a randomly selected sample of a larger area is called sampling. segments represent a sample. Gathering data from a randomly selected sample of a larger area is called sampling6. Find the .total number of sunflower plants for the 10 segment sample. This is an estimation based on a formula. Add all the grid segment sunflowers together and divide by ten to get an AVERAGE number of sunflower plants per grid segment. Record 5.th iFinds num theber itotaln the tnumberable. M uoflt ipsunflowerle the aver aplantsge num forber theof su 10nflo segmentwer plants sample.by 100 (th Thisis is t hise tanota lestimation number of g rbasedid segm onen ts)a formula.to find the Add total allnum theber gridof pl asegmentnts in the msunflowerseadow base dtogether on your sa andmp ledivide. Reco rbyd t htenis n utom bgeter inan yo AVERAGEur data table. number of sunflower plants per grid segment. Record this number in the table. Multiple the average number of sunflower plants by 100 (this is the total number of grid segments) to find the total number of plants in the 1 of 3 meadow based on your sample. Record this number in your data table. 3/19/14 11:36 AM

6. Now count all the sunflower plants actually shown in the meadow. Record this number in the data table. Divide this figure by 100 to calculate the average number of sunflower plants per each grid. Random Sampling http://www.biologycorner.com/worksheets/random_sampling.html

7. Now count all the sunflower plants actually shown in the meadow. Record this number in the data table. Divide this figure Results: by 100 to calculate the average number of sunflower plants per each grid.

Random Sampling Data Actual Data

Grid Sigment Number of Sunflowers (number - letter)

Total number of Sunflowers ______(count by hand)

Average number of Sunflowers (divide total by 10) Per grid _____

Total Number of Sunflowers

Average (divide total by 100)

Total number of plants in meadow

(multiply average by 100)

Analysis: Analysis: 1. Compare the total number you got for sunflowers from the SAMPLING to the ACTUAL count. How close are they? 1. Compare the total number you got for sunflowers from the SAMPLING to the ACTUAL count. How close are they? 2. Why was the paper-slip method used to select the grid segments?

2. Why was the paper-slip method used to select the grid segments? 3a. A lazy ecologist collects data from the same field, but he stops just on the side of the road and just counts the 10 segments near the road. These 10 segments are located at J 1-10. When he submits his report, how many sunflowers will he estimate are in the field? 3. a.) A lazy ecologist collects data from the same field, but he stops just on the side of the road and just counts the 10 segments near the road. These 10 segments are located at J 1-10. When he submits his report, how many sunflowers will he estimate are in the field? b. Suggest a reason why his estimation differs from your estimation.

4. Populab.)tio nSuggest Samplin ag reasonis usua llwhyy mo hisre e estimationffective wh ediffersn the p fromopula yourtion hestimation.as an even dispersion pattern. Clumped dispersion patterns are the least effective. Explain why this would be the case.

4. Population Sampling is usually more effective when the population has an even dispersion pattern. Clumped5. Describ dispersione how you wpatternsould use are Sa mthepl inleastg to deffective.etermine Explainthe popu whylatio nthis of dwouldandel iobens the in y case.our yard.

6. In a forest that measures 5 miles by 5 miles, a sample was taken to count the number of silver maple trees in the forest. The number of trees counted in the grid is shown below. The grids where the survey was taken were chosen randomly. Determine how many silver maple trees are in this forest using the random sampling technique. Show your work! 5. Describe how you would use Sampling to determine the population of dandelions in your yard.

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