Final answer:
The SQL query as provided will result in an error because it lacks necessary column specifications for the avg() function.
Step-by-step explanation:
The given SQL query attempts to select natcode from the stock table, joining it with the nation table on a common field, natcode. The query groups the results by stock.natcode and intends to filter these groups using a HAVING clause. However, the query is incomplete because the avg() function is not provided with a column to calculate the average, and in the subquery, the avg() function is also missing a column. Thus, the provided SQL query will result in an error since the necessary columns for the avg() function are not specified. The survey information unrelatedly indicates that the average increase for all NASDAQ stocks represents a population parameter.
The exercise information provided pertains to a statistical analysis of NASDAQ stocks, which may seemingly have no direct connection to the required SQL query. Referring to the provided information, the average increase for all NASDAQ stocks represents a population parameter since it is a measure of an entire group (population) rather than a portion (sample) and this information is contrasted with a statistic, which would be a measure of a sample.