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  1. Suppose that a radio contains six transistors, two of which are defective.
    Three transistors are selected at random, removed from the radio, and
    inspected. Let Y equal the number of defectives observed,where Y =
    0, 1, or 2. Find the probability distribution for Y . Express your results
    graphically as a probability histogram.
  2. Suppose that X has probability density function f (x) = 2x between 0 and
    1 and f (x) = 0 elsewhere. Compute V ar(X) and V ar(X
    2
    ).
  3. Suppose that Y possesses the density function
    f (y) =
    cy, 0 ≤ y ≤ 2
    0, elsewhere
    (a) Find the value of c that makes f (y) a probability density function.
    (b) Find F (y).
    (c) Use F (y) to find P (1 ≤ Y ≤ 2).
    (d) Use f (y) and geometry to find P (1 ≤ Y ≤ 2).
  4. The volume in a set of wine bottles is known to follow a N (µ, 25) distribution. You take a sample of the bottles and measure their volumes.How
    many bottles do you have to sample to have a 95% confidence interval for
    µ with width 1?
  5. Let Y1 and Y2 have joint density function:
    f (y1
    , y2) =
    e−(y 1 +y 2 ) , y1 > 0, y2 > 0,
    0, elsewhere
    what is:
    (a) P (Y1 < 1, Y2 > 5)?
    (b) P (Y1 + Y2 < 3)?
  6. Denote
    S
    0
    2 =
    P n
    i=1 (Yi − Y¯ )2
    n
    and S2 =
    P n
    i=1 (Yi − Y¯ )2
    n − 1
    .
    If the Yi are i.i.d. and normally distributed,
    (a) find V (S
    0
    2
    ).
    (b) show that V (S
    2
    ) > V (S
    0
    2
    ).
    (c) Therefore, which estimator do you prefer? Why?