DS-624 Quality Management
Chapter 11
B. Probability & Statistics
DS-624 Quality Management
What is Population on a statistical study?
What are Population parameters?
What is a Sample?
What are the components of the CLT?
Why is it important to know if a difference is statistical significant?
How to draw conclusions using statistics?
What are Descriptive Statistics?
What are Analytics (or Inferential) Statistics?
Population & Sample
What is Population on a statistical study?
Population refers to the collection of all items or data under consideration
What are Population parameters?
A parameter is a numerical value that provides information about the entire population. Example of parameters are mean and standard deviation.
What is a Sample?
It is a subset of the population. Samples are selected randomly so that they represent the population from which they are drawn.
Central Limit Theorem
The Central Limit Theorem (CLT) is an important principle used in statistical process control
What are the components of the CLT?
The mean of the sampling distribution of means is equal to the mean of the population from which the samples were drawn.
The variance of the sampling distribution of means is equal to the variance of the population from which the samples were drawn divided by the size of the samples.
If the original population is distributed normally (that is, it is bell shaped) the sampling distribution of means will also be normal.
Drawing Valid Statistical Conclusions
Why is it important to know if a difference is statistical significant?
Decisions can not be made just by “gut feeling”.
Comparing two scenarios merely by looking at the numbers maybe better than gut feeling but still not good enough.
Statistics is used to draw valid conclusions.
How to draw conclusions using statistics?
Draw representative samples from a homogeneous population
By analyzing the sample we draw conclusion about the population (CLT)
Descriptive vs. Analytical (Inferential) Statistics
What are Descriptive Statistics?
This consists of a set of collecting, organizing, summarizing, and presenting the data.
A descriptive study shows various properties of a set of data such as mean, median, mode, dispersion, shape, and so on.
Graphical tools include histograms, pie charts, box plots, and others.
Descriptive vs. Analytical (Inferential) Statistics
What are Analytics (or Inferential) Statistics?
This consists of a set of making inferences, hypothesis testing, and making predictions.
Uses data from a sample to make estimates of inferences about the population from which the sample was drawn.
Use tools such as hypothesis testing and scatter diagrams to determine the relationships between variables and male predictions using regression equations.
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