The porosity of a concrete block is a measure (as a percentage) of the amount of empty space in the.

  The porosity of a concrete block is a measure (as a
percentage) of the amount of empty space in the block. In residential homes
with concrete-block foundations, a larger porosity leads to damper, colder
basements. A contractor recommends pretreatment of concrete blocks with a
product designed to decrease the porosity. A random sample of concrete blocks
was obtained, and the porosity of each was measured. The clear, paintlike
product was applied to each block, and the porosity was measured again. The
differences (before treatment – after treatment) in porosities were recorded.
Assume normality. Is there any evidence to suggest the new product decreases
the mean porosity of concrete blocks?

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Each employee hired at an electronics parts assembly line in
Edmonton, Alberta, is given a general intelligence test. To determine which
method of training is more effective, eight pairs of new hires were matched
according to their exam scores. One set of employees was asked to read
appropriate training manuals, while the other group watched interactive
training videos. Each employee was then asked to assemble a part used in a
locater-beacon transmitter, and the time (in minutes) to completion was
recorded. The data are given in the following table.

Description: Table

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Description: Graphical user interface, text, application

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