Answer the following questions 1. Why is there no Q-test for n -2? Pick two numb

Question

Answer the following questions 1. Why is there no Q-test for n -2? Pick two numbers at random and calculate both Qi and Qo. Use the results of your calculations to answer the question. 2. We have used parts-per-thousand (ppt) calculations of the deviations in this experiment, but we could also have used parts-per-hundred (pph) or parts-per-million (ppm). Usually we choose a calculation that gives answers between 1 and 100 for convenience. What would the formulas be for pph and for ppm? pph: ppm: If ppt 0.011, then pph- and ppm What is another name for pph? 95 Exp. 7-Analysis of Data

Explanation / Answer

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Accuracy refers to the closeness of a measured value to a standard or known value. For example, if in lab you obtain a weight measurement of 3.2 kg for a given substance, but the actual or known weight is 10 kg, then your measurement is not accurate. In this case, your measurement is not close to the known value.

Precision refers to the closeness of two or more measurements to each other. Using the example above, if you weigh a given substance five times, and get 3.2 kg each time, then your measurement is very precise. Precision is independent of accuracy. You can be very precise but inaccurate, as described above. You can also be accurate but imprecise.

For example, if on average, your measurements for a given substance are close to the known value, but the measurements are far from each other, then you have accuracy without precision.

A good analogy for understanding accuracy and precision is to imagine a basketball player shooting baskets. If the player shoots with accuracy, his aim will always take the ball close to or into the basket. If the player shoots with precision, his aim will always take the ball to the same location which may or may not be close to the basket. A good player will be both accurate and precise by shooting the ball the same way each time and each time making it in the basket.

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Measurement Systems Analysis (MSA) is a type of experiment where you measure the same item repeatedly using different people or pieces of equipment. MSA is used to quantify the amount of variation in a measure that comes from the measurement system itself rather than from product or process variation. It assesses a measurement system for some or all of the following four characteristics:

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