Random Sampling

Random Sampling Data Actual Data Grid Segment (number and letter) Number of Sunflowers Total number of Sunflowers _228_____ (count by hand) Average number of Sunflowers (divide total by 10) Per grid __22.8___ C8 2 J8 0 D10 2 C9 2 G7 3 G6 1 D2 2 F9 3 G1 3 D10 2 Total Number of Sunflowers 20 Average (divide total by 10) 2 Total number of plants in meadow (multiply average by 100) 200 8. 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. Analysis 1. Compare the total number you got for sunflowers from the SAMPLING to the ACTUAL count. How close are they? I estimated that there were 200 sunflowers in the meadow. The actual count was 228. I would say for an estimate this is close enough given a margin of error. 2. Why was the paper-slip method used to select the grid segments? The paper slip method was used because it keeps it random. There is no way to skew the results when you are pulling random numbers or letters out of a bowl. 3. A lazy ecologist collects data from the same field, but he stops just on the side of the road and just counts the ten segments near the road. These ten segments are located at J, 1-10. When she submits her report, how many sunflowers will she estimate are in the field? There are 7 sunflowers in that row. With her estimation the meadow would only have 70 sunflowers in it which is extremely off count. 4. Suggest a reason why her estimation differs from your estimation. Many times the outskirts of a meadow are thinner than the inside. By taking it only from the outskirts it is no longer random and is a focused study. 5. Population sampling is usually more effective when the population has an even dispersion pattern. Clumped dispersion patterns are the least effective. Explain why this would be the case. Random sampling won’t work well if there is a clumped dispersion because it throws of the count and is hard to get an average per grid. 6. Describe how you would use sampling to determine the population of dandelions in your yard. I would use this same technique. I would form a grid on my yard and then use the paper slip method to count certain areas in my yard. 7. In an area that measures five miles by five miles, a sample was taken to count the number of desert willow trees. The number of trees counted in the grid is shown below. The grids where the survey was taken were chosen randomly. Determine how desert willow trees are in this forest using the random sampling technique. Show your calculations. 35 divided by 5 = 7 trees per grid divide that by 35 = 5 x 35= 175 trees in the meadow 7 3 5 11 9 Reference Biology Corner. Random Sampling. 2014 Apr 6. Web.