TABLE 10-14
a Problem with a Telephone Line That Prevents $$\text { t-Test: Two- Sample Assuming Unequal Variances }$$

question 152

Short Answer

TABLE 10-14
A problem with a telephone line that prevents a customer from receiving or making calls is disconcerting to both the customer and the telephone company. The data on samples of 20 problems reported to two different offices of a telephone company and the time to clear these problems (in minutes) from the customers' lines are collected. Below is the Excel output to see whether there is evidence of a difference in the mean waiting time between the two offices assuming that the
population variances in the two offices are not equal.
$$\text { t-Test: Two- Sample Assuming Unequal Variances }$$
$$\begin{array} { l r r } & \text { Office 1 } & \text { Office 2 } \\\hline \text { Mean } & 2214 & 2.0115 \\\text { Variance } & 2.951657 & 3.57855 \\\text { Observations } & 20 & 20 \\\text { Hypothesized Mean Difference } & 0 & \\\mathrm { df } & 38 & \\\mathrm { t } \text { Stat } & 0.354386 & \\\mathrm { P } ( \mathrm { T } < = \mathrm { t } ) \text { one- tail } & 0.362504 & \\\mathrm { t } \text { Critical one- tail } & 1.685953 & \\\mathrm { P } ( \mathrm { T } < = \mathrm { t } ) \text { two- tail } & 0.725009 & \\\mathrm { t } \text { Critical two-tail } & 2.024394 & \\\hline\end{array}$$

-Referring to Table 10-13, construct a 95% confidence interval estimate of the difference in proportion between the Kohler and Russell disks that are defective.

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Definitions:

Antibodies

Proteins produced by the immune system to identify and neutralize foreign objects such as bacteria and viruses.

Immune System

The complex network of cells, tissues, and organs that work together to defend the body against attacks by foreign invaders, like bacteria and viruses.

Myelination

The process of forming a myelin sheath around neurons, improving the speed and efficiency of electrical signal transmission in the nervous system.

Schwann Cells

A type of glial cell that myelinates the axons of the peripheral nervous system, enabling fast electrical impulses.