The Centers for Disease Control and Prevention reported that…

The Centers for Disease Control and Prevention reported that 20% of preschool children lack required immunizations, thereby putting themselves and their classmates at risk.  Use the normal distribution to approximate the probability that in a group of 64 children, at least 12 children are without immunizations. Make sure to check the conditions that allow a normal distribution to approximate a binomial distribution.

Seventy-two individuals selected at random responded indepen…

Seventy-two individuals selected at random responded independently when asked whether food stamps should be restricted to families who earn below the level of $12,000 per year for a family of four. A survey indicates that 70% of the population favors such proposition.  If the survey results are correct, use the Normal distribution to estimate the probability that in a sample of 72, less than 44 will support the proposition. Make sure to check the conditions that allow a normal distribution to approximate a binomial distribution.

The length of life (in hours) of a certain type of electric…

The length of life (in hours) of a certain type of electric bulb is a continuous random variable with a mean of 500 hours and a standard deviation of 35 hours.  Draw the bell-shaped curve and label it. Use the central limit theorem to find the probability that a random sample of 49 bulbs will have a mean life between 488 and 505 hours.

A 50 MVA, 230 kV (WYE) / 23 kV (DELTA) three-phase transform…

A 50 MVA, 230 kV (WYE) / 23 kV (DELTA) three-phase transformer has the following parameters R1   =0.30 ohm, X1 = 0.65 ohm;    R2 = X2 = 0.0 ohm Assume the core has infinitive impedance. Note, subscript 1 refers to the primary 230 kV side. At the 230 kV side a three-phase Y load is connected. The voltage at the load is 220 kV at 30 degrees, and the load absorbs, current flow at the load, is 5 kA amps at 0 degrees.  What is the magnitude of the voltage at the 23 kV, terminals? Enter your answers in kV, thus 23,206 V @/15 degrees enter as 23.21 Note that the word kV is not entered, just the numbers, enter two decimal places.