A point estimate is one number used to estimate an unknown population parameter. Because surveying an entire population is usually impractical, a sample provides a workable, imperfect estimate. section 5.2
Sleep survey
Suppose a survey of 45 people finds an average of 6.5 hours of sleep last night. The sample mean, 6.5 hours, becomes the point estimate for the population’s mean sleep time. section 5.2
A single sample cannot reveal exactly where its mean lies among all possible sample means. Treat the point estimate as useful but uncertain, then use a confidence interval to infer a plausible range for the population mean. section 5.2
