A dust mite allergen level that exceeds 2 micrograms per gram (mg/g) of dust has been associated with the development of allergies. Consider a random sample of four homes and let Y be the number of homes with a dust mite level that exceeds 2 mg/g. The probability distribution for Y=y, based on a study by the National Institute of Environmental Health Sciences, is shown in the following table.

y 0 1 2 3 4
p(y) .09 .30 .37 .20 .04

(a) Find the probability that three or four of the homes in the sample have a dust mite level that exceeds 2 µg/g.
(b) Find the probability that fewer than three homes in the sample have a dust mite level that exceeds 2 µg/g.

(a) 0.24

(b) 0.76

Step-by-step explanation:

We are given that let Y be the number of homes with a dust mite level that exceeds 2 mg/g. The probability distribution for Y=y is shown below ;

     y                 P(y)

     0                 0.09

     1                  0.30

     2                 0.37

     3                 0.20

    4                  0.04

(a) Probability that three or four of the homes in the sample have a dust mite level that exceeds 2 µg/g = P(y = 3) + P(y = 4)

                                           = 0.20 + 0.04 = 0.24 .

(b) Probability that fewer than three homes in the sample have a dust mite level that exceeds 2 µg/g = P(y = 0) + P(y = 1) + P(y = 2)

                                           = 0.09 + 0.30 + 0.37 = 0.76 .

The correct answer to this open question is the following.

Although there are no options attached, we can say the following.

Faults, folding, ridges, mountains, valleys, and volcanic arcs are formed when the plates move because they are the result of the collision of plates in the underground. Scientists have a name for this phenomenon. They called it subduction zones. Here the plates collide creating a formidable force that generates earthquakes. Subduction zones are regions on planet Earth when tectonic plates collide and form new physical structures. For instance, mountain chains are formed throughout the years after these tremendous collisions.