The variance is a figure that represents how far the data in your sample is clustered around the mean.  This figure will give you an idea of how far your data is spread out. Samples with low variance have data that is clustered closely about the mean. Samples with high variance have data that is clustered far from the mean. Variance is often used to compare the distribution of two data sets. This will give you a figure of how much each data point differs from the mean.  For example, in our sample of test scores (10, 8, 10, 8, 8, and 4) the mean or mathematical average was 8. 10 - 8 = 2; 8 - 8 = 0, 10 - 8 = 2, 8 - 8 = 0, 8 - 8 = 0, and 4 - 8 = -4. Do this procedure again to check each answer. It is very important you have each of these figures correct as you will need them for the next step. You will need each of these figures to find out the variance in your sample.  Remember, in our sample we subtracted the mean (8) from each of the numbers in the sample (10, 8, 10, 8, 8, and 4) and came up with the following: 2, 0, 2, 0, 0 and -4. To do the next calculation in figuring out variance you would perform the following: 22, 02, 22, 02, 02, and (-4)2 = 4, 0, 4, 0, 0, and 16. Check your answers before proceeding to the next step. This figure is called the sum of squares.  In our example of test scores, the squares were as follows: 4, 0, 4, 0, 0, and 16. Remember, in the example of test scores we started by subtracting the mean from each of the scores and squaring these figures: (10-8)^2 + (8-8)^2 + (10-8)^2 + (8-8)^2 + (8-8)^2 + (4-8)^2 4 + 0 + 4 + 0 + 0 + 16 = 24. The sum of squares is 24. Remember, n is how many numbers are in your sample. Doing this step will provide the variance. The reason to use n-1 is to have sample variance and population variance unbiased.    In our sample of test scores (10, 8, 10, 8, 8, and 4) there are 6 numbers. Therefore, n = 6. n-1 = 5. Remember the sum of squares for this sample was 24. 24 / 5 = 4.8 The variance in this sample is thus 4.8.
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One-sentence summary -- Find the variance. Subtract the mean from each of your numbers in your sample. Square all of the numbers from each of the subtractions you just did. Add the squared numbers together. Divide the sum of squares by (n-1).

Q: Use your crescent wrench to turn the metal tab back to the on position. The metal tab should now run parallel to the incoming line from the gas supplier. Once the gas is turned on, go back to the line and turn its valve on as well. If you do not turn the gas line on, then you will not be able to test for any possible leaking. Put a 50/50 mixture of dish soap and water into a spray bottle and shake it. Spray the mixture onto the gas cap. If you do not see any bubbles, then the cap is installed correctly. However, if you see bubbles appear around the cap that means the gas is leaking. Repeat the steps until there is no leak. Besides looking for bubbles, listen for gas escaping. It will sound like hissing. You may need to relight the pilot light on your water heater and on other appliances since you turned off the gas.
A: Turn the main gas back on. Turn the gas line on. Check for leaks. Relight pilot lights.

Article: Although fire and smoke are typically accidental occurrences, avoid placing books in a room or corner susceptible to smoke or fire exposure. Books should not be placed in a room adjacent to a fireplace or wood-burning stove, nor should they be in an area prone to steam, such as a kitchen, laundry room, or bathroom. Refrain from storing books in a room prone to extreme temperatures. Hot rooms might include laundry rooms, kitchens, and sunrooms, while cold rooms might include a garage, pantry, laundry room, or similarly poorly-insulated area. The ideal temperature for books is between 65 and 72 degrees F (or 18-22 degrees C). Keep this in mind when choosing a designated storage area for your collection. Rough shelving such as particle board can damage the binding of books, while chemically-treated or painted shelves can leach into books, causing staining, disintegration, or weakening of the binding’s fibers. When choosing a case or shelf, look for smooth, sealed wood intended for indoor use, or smooth, enameled metal. Harsh, intense light, whether from the sun or from a bulb, can cause fading and damage to rare and old books. Choose a space not regularly touched by the sun, and avoid placing heavy overhead lighting beside your books. They will thrive best in a darker environment, such as a corner or interior room. Whether you plan to place your books in an open bookshelf, or a closed case, make sure the area has been cleaned before placing your books into it. Remove any dust from shelves, and wipe down all surfaces. Cleaning the top of your bookshelf has the potential to rain dust upon your tomes, so make sure every possible surface of your shelf or case has been thoroughly scrubbed.
Question: What is a summary of what this article is about?
Eliminate fire and smoke hazards. Avoid extreme temperatures and conditions. Select a wooden or metal bookcase. Dim harsh lighting. Clean your storage space thoroughly.

Article: Stand with your non-dominant foot in front with your toes facing forward. Your dominant foot should be in the back with toes pointed slightly out.  Shift your weight to your dominant foot. Make sure your hips are facing straight forward, not angled to the side. Cup your non-dominant hand slightly and place the ball in it. Make sure the ball securely balanced so it won't wobble or fall out of your hand.   Keep your fingers slightly loose to distribute the weight of the ball.  This will help it stay balanced. Don't grip the ball with your fingers.  You want it to be stable, but it still has to be able to fly out of your hand when you hit it. Bring the arm holding the ball across to the side of your body in front of your hitting arm.  The ball should be at the height of your mid-thigh.   Straighten the arm with the ball in it, and move it to the side by shifting your arm at the shoulder, not the elbow. You want the ball to be low so that you can put more power into it as you move your whole body forward and up. Move your hips back and keep your upper back straight as you bring your shoulders towards the ball.  This brings your a little closer to the ball so that you have more control.  Don't hunch over but make sure you aren't standing up straight. As your hips move back, you can raise the toes on your front foot so your heel is touching the ground and your toes are pointing up.
Question: What is a summary of what this article is about?
Get your feet into position. Ready the ball. Lower the ball. Lean your shoulders forward.