Explain in your own words what standard deviation is and why it is useful when describing experimental data. 2. What range for mass of the washers would you expect 68% of the samples to fall into? What about 95%? (Hint: use the standard deviation calculated for mass measurements) 3. Do you think that a sample population of two washers would have been adequate to generate the descriptive statistics for the entire population? Explain 4. For what reasons would someone generally NOT want to use the very end of a ruler for taking measurements. 5. Assume that the actual density of the washers is 7.81 g/cm3. What is the percent error of your calculated mean? What sources of error exist in this experiment?