Using the Chi-Square Critical Values Table



Using the Chi-Square Critical Values Table

The chi-square critical values table provides two values that you need to calculate chi-square:

|•|Degrees of freedom. This number is one less than the total number of classes of offspring in a cross. In a monohybrid cross, |

| |such as our Case 1, there are two classes of offspring (red eyes and sepia eyes). Therefore, there is just one degree of |

| |freedom. In a dihybrid cross, there are four possible classes of offspring, so there are three degrees of freedom. |

|•|Probability. The probability value (p) is the probability that a deviation as great as or greater than each chi-square value |

| |would occur simply by chance. Many biologists agree that deviations having a chance probability greater than 0.05 (5%) are not |

| |statistically significant. Therefore, when you calculate chi-square you should consult the table for the p value in the 0.05 |

| |row. |

Use the critical values table here to do the problems below. *

|Degrees of Freedom (df) |

|Probability (p) |1 |2 |3 |4 |5 |

|0.05 |3.84 |5.99 |7.82 |9.49 |11.1 |

|0.01 |6.64 |9.21 |11.3 |13.2 |15.1 |

|0.001 |10.8 |13.8 |16.3 |18.5 |20.5 |

The "mean" is the "average" you're used to, where you add up all the numbers and then divide by the number of numbers. It is represented by the symbol x.

The "median" is the "middle" value in the list of numbers. To find the median, your numbers have to be listed in numerical order, so you may have to rewrite your list first. It is represented by Md.

The "mode" is the value that occurs most often. If no number is repeated, then there is no mode for the list. It is represented by Mo.

The "range" is just the difference between the largest and smallest values. It is represented by R.

The “mid-range” is the range divided by 2. It is represented by MR.

Standard Deviation (SD) is the measure of spread of the numbers in a set of data from its mean value. It is also called as SD and is represented using the symbol σ (sigma). This can also be said as a measure of variability or volatility in the given set of data. Find the mean, variance and SD of the given numbers using this free arithmetic standard deviation calculator online. Enter an 'n' number of values in the calculator and find the SD (σ), mean and variance.

The standard error of the mean (SEM) estimates the variability between sample means that you would obtain if you took multiple samples from the same population. The standard error of the mean estimates the variability between samples whereas the standard deviation measures the variability within a single sample.

The 95% confidence interval is 2 times the standard deviation.

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