Black Thursday Iteration 1 - Business Intelligence

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Starting the Analysis Layer

Our analysis will use the data we constructed in iteration 1 to answer questions regarding data calculation.

But, who in the system will answer those questions? Assuming we have a SalesEngine instance called sales_engine, let’s initialize a SalesAnalyst like this:

sales_analyst = sales_engine.analyst

Then, answer the following questions:

How many products do merchants sell?

Do most of our merchants offer just a few items, or do they represent a warehouse?

sales_analyst.average_items_per_merchant # => 2.88

And what’s the standard deviation?

sales_analyst.average_items_per_merchant_standard_deviation # => 3.26

Note on Standard Deviations

There are two ways to calculate standard deviations – for a population, and for a sample.

For this project, use the sample standard deviation.

As an example, given the set 3,4,5. We would calculate the deviation using the following steps:

1. Take the difference between each number and the mean, then square it.
2. Sum these square differences together.
3. Divide the sum by the number of elements minus 1.
4. Take the square root of this result.

Or, in pseudocode:

set = [3,4,5]

std_dev = sqrt( ( (3-4)^2+(4-4)^2+(5-4)^2 ) / 2 )

Which merchants sell the most items?

Maybe we could set a good example for our lower sellers by displaying the merchants who have the most items for sale. Which merchants are more than one standard deviation above the average number of products offered?

sales_analyst.merchants_with_high_item_count # => [merchant, merchant, merchant]

What are prices like on our platform?

Are these merchants selling commodity or luxury goods? Let’s find the average price of a merchant’s items (by supplying the merchant ID):

sales_analyst.average_item_price_for_merchant(12334159) # => BigDecimal

Then we can sum all of the averages and find the average price across all merchants (this implies that each merchant’s average has equal weight in the calculation):

sales_analyst.average_average_price_per_merchant # => BigDecimal

Which are our Golden Items?

Given that our platform is going to charge merchants based on their sales, expensive items are extra exciting to us. So, which are our “Golden Items”, those items that are two standard deviations above the average item price? Return the item objects of these “Golden Items”.

sales_analyst.golden_items # => [<item>, <item>, <item>, <item>]