For any size data set, the standard deviation is a reliable statistic for reporting precision. There are two formulas for calculating standard deviation, with a very slight difference between them. You will use one formula if your measured data represents an entire population. You will use the second formula if your measured data is from only a sample of the population.  Your data represents an entire population if you have collected all the measurements possible from all possible subjects. For example, if you are conducting tests on people with some very rare disease, and you believe that you have tested everyone with that disease, then you have the entire population. The standard deviation formula in this case is: σ=Σ(x−μ)2n{\displaystyle \sigma ={\sqrt {\frac {\Sigma (x-\mu )^{2}}{n}}}}  A sample set is any group of data less than an entire population. This is actually going to be used more often. The standard deviation formula for a sample set is: σ=Σ(x−μ)2n−1{\displaystyle \sigma ={\sqrt {\frac {\Sigma (x-\mu )^{2}}{n-1}}}}  Notice that the only difference is in the denominator of the fraction. For an entire population, you will divide by n{\displaystyle n}. For a sample set, you will divide by n−1{\displaystyle n-1}. As with calculating the average deviation, you will begin by finding the mean of the data values. Using the same set of measurements as above, the mean is 12.4. For each data point, subtract the data value from the mean, and square that result. Because you are squaring these variations, whether the difference is positive or negative does not matter. The square of the difference will always be positive. For the five data values in this sample, these calculations are as follows:  (12−12.4)2=(−0.4)2=0.16{\displaystyle (12-12.4)^{2}=(-0.4)^{2}=0.16} (11−12.4)2=(−1.4)2=1.96{\displaystyle (11-12.4)^{2}=(-1.4)^{2}=1.96} (14−12.4)2=1.62=2.56{\displaystyle (14-12.4)^{2}=1.6^{2}=2.56} (13−12.4)2=0.62=0.36{\displaystyle (13-12.4)^{2}=0.6^{2}=0.36} (12−12.4)2=(−0.4)2=0.16{\displaystyle (12-12.4)^{2}=(-0.4)^{2}=0.16} The numerator of the standard deviation fraction is the sum of the squared differences between each value and the mean. To find this sum, add together the figures from the previous calculation. For the sample data set, these are: 0.16+1.96+2.56+0.36+0.16=5.2{\displaystyle 0.16+1.96+2.56+0.36+0.16=5.2} This is the one step that will differ for either a population calculation or a sample set calculation. For a full population, you will divide by n{\displaystyle n}, the number of values. For a sample set, you will divide by n−1{\displaystyle n-1}. This example has only five measurements and is therefore only a sample set. Thus, for the five values being used, divide by (5-1) or 4. The result is 5.2/4=1.3{\displaystyle 5.2/4=1.3}. At this point, the calculation represents what is called the variance of the data set. The standard deviation is the square root of the variance. Use a calculator to find the square root, and the result is the standard deviation. σ=1.3=1.14{\displaystyle \sigma ={\sqrt {1.3}}=1.14} Using this calculation, the precision of the scale can be represented by giving the mean, plus or minus the standard deviation. For this data, this will be 12.4±1.14.  The standard deviation is perhaps the most common measurement of precision. Nevertheless, for clarity, it is still a good idea to use a footnote or parentheses to note that the precision value represents the standard deviation.

Summary: Use the correct formula for standard deviation. Find the mean of the data values. Find the square of each variation. Calculate the sum of the squared differences. Divide by the data size. Find the square root of the result. Report your result.


Part of being sweet involves developing good manners, which in turn, involves avoiding bad ones, such as swearing. If you get angry or upset (or stub your toe) bite your tongue and try not to swear or curse. If you really must swear, stay away from any expletives, and say things such as "drat" or "darn" instead. Sweet people are nice people, and nice people generally like everyone—or at least act as though they like everyone. Try to refrain from insulting others or gossiping about them, and never bully anyone. Not only is this negative behavior, but it will show others that you are capable of thinking not-so-nice things about others. This, in turn, may cause those listening to you to wonder what you might think of them. Instead, either ignore the bully or pretend that you did not hear the insulting or swearing. Bullies want attention, and you will be giving them just that by reacting to them. Part of being sweet and kind is being approachable. You can achieve this through maintaining proper posture—this means that your back is straight, your head is held high, and your shoulders are thrown back slightly (but not to the extent of discomfort). Slouching, crossing your arms, and sticking your hands in your pockets will make you appear disinterested, anti-social, or upset, none of which are considered very sweet. Not only are drugs harmful to your body, but vandalism can get you in trouble with authority. Sweet people are well-behaved people, and thus tend not to get into trouble. Refrain from vandalizing and destroying property (be it private or public), and try not to do drugs. Some drugs, such as hallucinogens, can lead you to partake in destructive behavior, while other drugs can deteriorate or permanently damage your health.

Summary: Do not swear or curse. Do not insult, gossip, or bully. Do not react to bullying or swearing. Do not slouch, cross your arms, or put your hands in your pockets. Do not partake in drugs or destructive behavior.


You'll need to use the "Terminal" app to hide your folder.    This is in the top right corner of your screen. You can also hold ⌘ Command and tap Spacebar.     Your folder should now be hidden from view! Hidden folders on a Mac are invisible unless you type a specific command into Terminal.
Summary: Two-finger click your desktop. Click New Folder. Type in a name for your folder. Tap ⏎ Return. Click the magnifying glass icon. Type in "Terminal". Tap ⏎ Return. Type chflags hidden. Drag your folder into Terminal. Tap ↵ Enter.