A Cell Phone Service Provider Has Selected a Random Sample

question 47

Multiple Choice

A cell phone service provider has selected a random sample of 20 of its customers in an effort to estimate the mean number of minutes used per day. The results of the sample included a sample mean of 34.5 minutes and a sample standard deviation equal to 11.5 minutes. Based on this information, and using a 95 percent confidence level:

• A) the critical value is z = 1.96
• B) the critical value is z = 1.645
• C) the critical value is t = 2.093
• D) The critical value can't be determined without knowing the margin of error.

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Definitions:

Control Circuit

An electrical circuit designed to control the operation of another circuit or device, often involving relays, sensors, and switches.

Overcurrent Protection

Systems or devices designed to protect electrical circuits from damage caused by excess current, typically through the use of fuses or circuit breakers.

Overload Protection

A safety feature designed to protect electrical circuits from damage caused by excessive current flow, typically via circuit breakers or fuses.

Overload Unit

A device or component in electric motors designed to protect them from running over their designed load for too long, preventing overheating or damage.