2 Descriptive Statistics Flashcards
The foundation of monitoring performance or QC is __________ statistics.
descriptive
Comparing the ________ of the data is common, comparing the _______ can be even more powerful
center; spread
I. Measures of Center/Location
- Mean
- Median
- Mode
I. Measures of Center/Location: Mean, Median or Mode?
- The calculated average of a set of values or simply called the average. The sum of all data values is divided by the total number of data values.
- It is the most commonly used measure of location
Mean
I. Measures of Center/Location: Mean, Median or Mode?
- The value of the middle observation, when the set is arranged in rank order. It is the value that divides the data into half. It is often used for skewed data.
Median
I. Measures of Center/Location: Mean, Median or Mode?
- It is the most frequently observed value in a set of observations.
- It is not commonly used as a measure of the data’s center but is more often used to describe data that seem to have two centers (bimodal).
- There can be more than one, if two or more values are equally common. It is possible than in a set of data there is no mode at all.
Mode
II. Measure of Dispersion
- It indicates how the data are distributed or spread. The _______ represents the relationship of all the data points to the mean. Three commonly used descriptions
of spread are:
1._______
2. _______
3._________
spread; range; standard deviation; coefficient of variation.
II. Measure of Dispersion: Range, Standard deviation, Coefficient of variation or Variance?
- A measure of the spread or the dispersion of data points.
- It is the difference between the largest and the smallest observed value. Thus, only the largest and least data values are considered.
- This is often a good measure of dispersion for small samples of data.
- The ______ value of a data set is greatly influenced by the presence of just one unusually large or small value in the sample commonly referred to as an outlier.
Range; range
II. Measure of Dispersion: Range, Standard deviation, Coefficient of variation, or Variance?
- It measures the “spread”, “variation” or “ dispersion” of the set of data about the mean or the expected value. It is the most frequently used measure of
variation. - It is the square root of the variance, which is the average of the squared differences from the mean.
- Low value indicates data points which tend to be very close
to the mean, while a high value indicates data widely spread out over a large range of values
Standard deviation
II. Measure of Dispersion: Range, Standard deviation, Coefficient of variation, or Variance?
- It is defined as the ratio of the standard deviation to the mean value of the data used in the analysis. It is expressed as a percentage.
- Similarly, it is used to measure the spread or dispersion of a set of data in proportion to its mean.
- It is considered a relative measure of precision. Signifies random error or imprecision .
✓ The smaller the value, the more reproducible the results, meaning more values are closer to the mean. The higher the value, the greater the dispersion in the variable.
Coefficient of Variation
II. Measure of Dispersion: Range, Standard deviation, Coefficient of variation, or Variance?
- Average distance from the center of the data and every value in the data set. It is depicted by the symbol S^2
Variance
III. Measures of Shape
- While there are many different “shape” distributions that data sets can exhibit, the most commonly discussed is the ________________ or Normal distribution curve.
Gaussian distribution
III. Measures of Shape
- The _______________ describe many continuous laboratory variables and shares several unique characteristics: the mean, median, and mode are identical; the distribution is ________ which means that half of the values fall to the left of the mean and the other half to the right. The symmetrical
shape is often called a “________”.
gaussian distribution; symmetric; bell curve
III. Measures of Shape
The gaussian curve is defined as a ___________ curve representing the normal distribution . It is a continuous function which approximates the exact ________ distribution of events.
symmetrical; binomial
III. Measures of Shape; Gaussian curve:
- The ________ of the distribution should be centered on the MEAN (best estimate of the true value)
peak
