Age-related macular degeneration (AMD) is a common eye disease among the elderly that can lead to partial or total loss of vision. It is well known that smoking and excessive weight tend to be associated with higher incidence rates of AMD. More recently, however, several genes have been found to be associated with AMD as well. One gene that has been considered is the Y402H gene. There are three genotypes for the Y402H gene—TT, TC, and CC. The relationship between AMD and the Y402H genotype is as follows: Y402H AMD=yes AMD=no TT (wild type) 41 380 YC 119 527 CC 121 278 Total 281 1185 (1) What is the relative risk for AMD for the CC genotype compared with the TT genotype?
Addition Rule of Probability
It simply refers to the likelihood of an event taking place whenever the occurrence of an event is uncertain. The probability of a single event can be calculated by dividing the number of successful trials of that event by the total number of trials.
Expected Value
When a large number of trials are performed for any random variable ‘X’, the predicted result is most likely the mean of all the outcomes for the random variable and it is known as expected value also known as expectation. The expected value, also known as the expectation, is denoted by: E(X).
Probability Distributions
Understanding probability is necessary to know the probability distributions. In statistics, probability is how the uncertainty of an event is measured. This event can be anything. The most common examples include tossing a coin, rolling a die, or choosing a card. Each of these events has multiple possibilities. Every such possibility is measured with the help of probability. To be more precise, the probability is used for calculating the occurrence of events that may or may not happen. Probability does not give sure results. Unless the probability of any event is 1, the different outcomes may or may not happen in real life, regardless of how less or how more their probability is.
Basic Probability
The simple definition of probability it is a chance of the occurrence of an event. It is defined in numerical form and the probability value is between 0 to 1. The probability value 0 indicates that there is no chance of that event occurring and the probability value 1 indicates that the event will occur. Sum of the probability value must be 1. The probability value is never a negative number. If it happens, then recheck the calculation.
Age-related macular degeneration (AMD) is a common eye
disease among the elderly that can lead to partial or total loss
of vision. It is well known that smoking and excessive weight
tend to be associated with higher incidence rates of AMD.
More recently, however, several genes have been found to
be associated with AMD as well. One gene that has been
considered is the Y402H gene. There are three genotypes
for the Y402H gene—TT, TC, and CC. The relationship
between AMD and the Y402H genotype is as follows:
| Y402H | AMD=yes | AMD=no |
| TT (wild type) | 41 | 380 |
| YC | 119 | 527 |
| CC | 121 | 278 |
| Total | 281 | 1185 |
(1) What is the relative risk for AMD for the CC genotype compared with the TT genotype?
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