alleryStart learning →To read a probability out of a z-table by hand, what do you work out before opening the table?
AThe median of the data
BThe range of the data
CThe mode of the data
DThe z-score of the value
Answer & Solution
Correct answer: D. The z-score of the value
1. A z-table is indexed by z-scores, not by raw data values.
2. So the raw value has to be standardised first.
3. Compute its z-score, then find that z-score in the z-column and read off the area.
4. The median is never needed, since the table already assumes a normal shape.
_Source: OpenStax High School Statistics (CC BY 4.0), Ch 6 "The Normal Distribution", section 6.2 Using the Normal Distribution_
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