Statistical Methods Flashcards

A process has a mean of 50 and a standard deviation of 5. What percentage of data falls within one standard deviation of the mean (45 to 55) in a normal distribution?

Answer: 68%

In a normal distribution, approximately 68% of data falls within ±1 standard deviation of the mean.

Which type of data can be ranked but does not have equal intervals between values?

Answer: Ordinal data

Ordinal data can be ranked in order, but the differences between ranks are not necessarily equal.

A run chart shows 8 consecutive data points above the centerline. This is an indicator of:

Answer: A special cause

Eight or more consecutive points on one side of the centerline signal a non-random pattern indicating a special cause.

What does a p-chart monitor in statistical process control?

Answer: Proportion of defective units

A p-chart tracks the proportion (fraction) of nonconforming (defective) units in a sample.

Which measure of central tendency is most affected by extreme outliers?

Answer: Mean

The mean is calculated using all values, so extreme outliers pull it significantly toward them.

A scatter diagram shows data points forming a tight cluster sloping downward from left to right. This indicates:

Answer: Strong negative correlation

A downward sloping tight cluster indicates a strong negative correlation between the two variables.

In a histogram, what does it mean when the distribution is skewed to the right?

Answer: The tail extends to the right with a few high values

Right skew means the tail is on the right side, indicating a few unusually high values pulling the distribution.