Final answer:
In many scientific fields, repeatability is often considered at a threshold of less than 5% uncertainty, with certain precise instruments achieving even lower uncertainty, like 0.011% for a triple-beam balance measurement.
Step-by-step explanation:
The question of at what percentage uncertainty results are deemed repeatable is a matter of context and specific scientific or engineering needs. However, a common benchmark in many scientific disciplines for repeatable results is less than 5% uncertainty. For instance, in the 17th question referenced, the percent uncertainty in a measurement of 0.445 kg using a triple-beam balance with an uncertainty of 0.05 g is calculated to be 0.011%, which is well below the threshold for good repeatability. In the context of confidence intervals, such as creating a 99 percent confidence interval, a higher confidence level implies a wider interval and vice versa; thus, decreasing the confidence level from 99 percent to 90 percent would result in a narrower confidence interval, holding all else constant.