Refer to dataset Cell_phones.xlsx and use R to answer this question.

Time

1554

1764

1578

1692

1560

1668

1512

1662

1812

1590

1632

1632

1614

1728

1578

1638

1632

1746

1632

1578

1704

1608

1482

1536

1578

1542

1698

1692

1686

1596

1662

1488

1506

1590

1644

1464

1578

1518

1590

1548

1608

1536

1572

1752

1626

1584

1554

1554

1614

1518

1578

1542

1698

1692

1686

1596

1662

1488

1506

1602

A time study of a large production facility was undertaken to determine the mean time required to assemble a cell phone. A random sample of the times to assemble 60 cell phones was recorded in seconds. An analysis of the assembly times reveals that they are normally distributed with a standard deviation of 78 seconds. Estimate with 90% confidence the mean assembly time for all cell phones. Report the Lower Bound ____________ and the upper bound _________________.

Refer to the Cell_phones dataset and use R to answer this question. Report 2 values after the decimal point and do not add commas to separate thousands (for example: 1312.34).

Estimate a 99% confidence interval for the mean assembly time for all cell phones. Report the Lower Bound __________________ and the upper bound ___________________.

Refer to the Cell_phones problem. Interpret the estimates you calculated in a sentence each (95% and 90%), and determine which one is wider and why.