The purpose of this lab is to become familiar with key terms and calculations used in conducting ecological experiments. Use excel please. Lab #1 – The Nature of Data Key Terms: Population – Sample – Variable – Statistic – Data set – Measures of central tendency: Mean – Mode – Median – Variation: Range – Variance – Standard deviation – Exercise #1 – Variation in a data set Table 1. Lengths of fishes caught. 78 69 63 75 69 52 54 40 9 64 65 63 62 69 52 60 67 72 73 27 Exam the data in Table 1 2. These data represent measurements of lengths of fish of 20 fish randomly caught and measured. Notice that all fishes are not the same length 3. Rearrange the data from lowest to highest value Questions

1. Do the fish lengths shown in table 1 appear to be simply random numbers? If not what pattern or tendency do you detect?

2. What factors might cause variation in fish length for a fish species?

3. How would you sample fish to test one of those influences on total length? Calculate and record the mean. Mean _____

4. Are any of the fish length measurements the same as the mean? 5. How many fish were longer than the mean? 6. How many fish were shorter than the mean? 7. Does the mean always describe the “typical measurement? Why or why not Calculate and record the median and the mode. Median______ Mode______ 8. In the sample, the mean differs from the median. What is responsible for this difference between the mean and the median? 9. How would the mean change without the 9 cm measurement? 10. How would the median change without the 9 cm fish measurement? 11. How would the mode change without the 9 cm fish measurement?

#fish #length #measurements

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