Standard Deviation and Standard Error Worksheet You will want to complete this worksheet before you do the inquiry lab, “Why Don’t Whales Have Legs?”. It will help you to write a procedure that has enough data to analyze … hint: multiple trials. Part 1: Watch the BozemanScience tutorial on Standard Deviation at http://www.bozemanscience.com/standarddeviation Part 2: Watch the BozemanScience tutorial on Standard Error at http://www.bozemanscience.com/standard-error Part 3: Complete the examples below. The formula for standard deviation is: Symbol Key ∑ = ‘sum of’ xi = the data point n = size of sample Lets start with a hypothetical data set. Below is a chart of the wingspan of 5 Painted Lady butterflies. They were all fed the same food as larvae and are the same age. Step 1: Calculate the mean wingspan and record the mean in each box in the column marked ‘mean’. To calculate the mean add all of the wingspan measurements together and divide by 5. Step 2: Subtract the wingspan of butterfly #1 from the mean. Record this number in the next column. Step 3: Repeat step 2 for each butterfly. Step 4: Square the calculation of the difference and record it in the next column. Repeat for each butterfly. Step 5: Add all of the squares of the differences together. Step 6: Total the number of samples and subtract 1 Step 7: Plug the numbers into the formula above for standard deviation and get the square root. This is your standard deviation! Butterfly # Wingspan Mean Difference between data point and mean (mm) 1 2 3 4 5 Calculation: 38 52 45 48 61 The following is the formula for standard error Use the data from the previous example to find standard error. Step 1: Calculate the square root the number of samples Step 2: Divide the standard deviation by the square root of the number of samples. Calculation: You will need to be able to calculate standard deviation and standard error for the “Why Don’t Whales Have Legs” lab.