In this task, You are given an open-domain question that can be answered based on factual information. Your task is to provide \*short\* answer (in a few words only) for the given question. The short answer can be one or more entities or it can also be boolean \*yes\* or \*no\*.
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Question: when did mount saint helens blow its top

Answer: May 18, 1980


Question: when did 'open era' began in tennis

Answer: 1968


Question: the ability of an instrument of actually measure what it is intended to measure is known as

Answer:
Construct validity