• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Determining the relationship between sample size and margin of error

Extracts from this document...


Determining the Relationship between Sample Size and Margin of Error 10 November 2008 PURPOSE To determine the effect of sample size on the amount of error in a population estimate obtained by capture, mark and recapture techniques. HYPOTHESIS When comparing two different samples from the same population, the null hypothesis is used. The null hypothesis expects that there is no difference between samples of different sizes. DATA PROCESSING AND COLLECTION The estimated population size was calculated using the Lincoln Index: For all rounds (in all trials) the number of individuals initially caught and markers was 20. In each round, the number of individuals recaptured as well as recaptured and marked differed. Sample population estimate calculation (for trial 1, round 1): Sample 1 (individuals initially caught) = 20 Sample 2 (individuals recaptured) = 10 Individuals recaptured and marked = 1 The actual population size was obtained by counting all members of the population in the sample area. The margin of error between the estimated population size and the actually population was determined by using the formula for percentage error: Sample percentage error calculation (for trial 1, round 1): These calculations have been used to produce Table 1. ...read more.


The curves of best fit for all four trials have a similar shape; initially the percentage error is high, but as sample size increases the error decreases. However, the data for each trial does not clearly follow the curve of best fit, which raises doubt on the accuracy of the trend suggested by the curve of best fit. Though to determine a curve that is more representative of a general trend, an average percentage error in population estimate for each sample size (for all four trials) must be taken. Sample calculation for average percentage error in population estimate for sample size of 10: Table 2: Average percentage error in population estimate (all four trials): Recapture Sample Size 10 15 20 25 30 Average percentage error in population estimate (%) 33.3 16.6 27.8 18.8 6.3 The averaged values in table 2 take into account all three trials and now can be graphed as a single set of points on a scatter plot. Figure 2: Average relationship between sample size and percentage error in population estimate The curve of best fit for the average data is similar in shape to the curves in figure 1. ...read more.


Other inaccuracies could have occurred because the sample sizes were relatively small. The first sample of 20 individuals in the initial capture (constant for all rounds in the experiment) could have been greater and for the second sample (the recapture sample which varied in each round), a greater number of sample sizes should have been considered to determine how far the trend continues. Lastly, since this experiment was carried out using beans in a container, the shape of the container prevented that sampling from being truly random. The beans on the bottom of the container were covered by many other beans and were rarely chosen in the sampling. To correct this, all the beans could have been laid out on a flat surface, where they would randomly be selected. Although natural human error would still exist, this method would be more representative of a sampling in a terrestrial ecosystem. Therefore, to improve this experiment more trials should be considered, a greater number of samples should be taken and the selection of individuals should take on a flat surface where each individual has an equal chance of being selected. 1 "Sample Size Calculator." 2004. Raosoft. 1 Nov 2008 <http://www.ezsurvey.com/samplesize.html>. ?? ?? ?? ?? 2 ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our International Baccalaureate Biology section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related International Baccalaureate Biology essays

  1. Yeast Population

    So, in this experiment the temperature used was simply room temperature. Type of Beaker: To let the yeast population grow within the given time, we used the same type of beaker. This was to decrease the amount of inaccuracy. Even if there was an error in the beaker, it will

  2. A Local Ecosystem, Patterns in Nature,Life on Earth,The Australian Biota ...

    One species, the parasite is benefited by the relationship while the other, the host is disadvantaged. An example of this includes the tapeworm living inside a mammal. The tapeworm is protected and is supplied with food, while the mammalian host suffers from a loss of nutrients.

  1. Adaptation and Natural selection

    Clean the snails by water once or twice 7) Let the snails dry 8) Put them on the paper 9) Take a picture of the snails on both shores Data processing: In this table shows the statistics, total number, average and standard deviation of both shores �lftanes and K�pavogur.

  2. Calibration curve

    In the same way this process must be continued until the last test tube ( I.E. test tube labelled '10') no distilled water is added. Therefore the total amount of liquid in each test tube is 10ml so far. 5.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work