**Bivariate Data and Covariance:**

Bivariate data refers to a set of data consisting of two variables, denoted as x and y, with corresponding observations. Covariance measures the relationship between these two variables and provides information about how they vary together.

**Given Information:**

In this problem, we are given the following information:
- cov(x, y) = 20
- variance of x = 16
- sum of squares of deviation of y from its mean = 250

**Calculating the Number of Observations:**

To determine the number of observations for this bivariate data, we need to use the given information and make use of relevant formulas. Let's break down the solution into steps:

**Step 1: Finding the Mean of y**

The sum of squares of deviation of y from its mean is given as 250. This information allows us to calculate the variance of y. The formula for variance is:

Variance of y = sum of squares of deviation of y from its mean / number of observations

Let's assume the number of observations as 'n' for now.

Variance of y = 250 / n

**Step 2: Finding the Covariance of x and y**

The covariance between x and y is given as 20. The formula for covariance is:

cov(x, y) = sum of [(xi - mean of x) * (yi - mean of y)] / number of observations

Since we know the covariance, we can rearrange the formula as follows:

20 = sum of [(xi - mean of x) * (yi - mean of y)] / n

**Step 3: Finding the Mean of x**

The variance of x is given as 16. Using the formula for variance, we have:

Variance of x = sum of squares of deviation of x from its mean / number of observations

16 = sum of squares of deviation of x from its mean / n

**Step 4: Rearranging the Equations**

To solve for the number of observations, we need to rearrange the equations derived from steps 1, 2, and 3.

From Step 1:
250 / n = Variance of y

From Step 2:
20 = sum of [(xi - mean of x) * (yi - mean of y)] / n

From Step 3:
16 = sum of squares of deviation of x from its mean / n

**Step 5: Solving the Equations**

To solve for n, we can substitute the expressions for variance of y and variance of x into the equation derived from Step 2:

20 = sum of [(xi - mean of x) * (yi - mean of y)] / (250 / n)

Simplifying further, we have:

20 = sum of [(xi - mean of x) * (yi - mean of y)] * (n / 250)

**Conclusion:**

To determine the number of observations for this bivariate data, we need to solve the equation derived from Step 5. This equation can be solved by rearranging and isolating the variable 'n'.

Please note that the solution provided here is a general approach to solving the problem. It assumes that the data follows a specific distribution or pattern. In real-world scenarios, additional information or assumptions might be required to arrive at an accurate solution.