A natural experiment is a chance occurrence that mimics a randomized controlled trial. In order to analyze causal effects from natural experiments, economists make use of a statistical method known as instrumental variables, in which one variable from a natural experiment is used as an instrument for a particular independent variable of interest. Assume the independent variable of interest is x1 and the dependent variable in a regression is y. Which of the following represent necessary characteristics of a suitable instrument? a. The instrument has at least 200 observations
b. The instrument is correlated with
c. The instrument has a conditional mean of zero
d. The instrument does not directly influence y, except through

What cylinder head operation is the technician performing in this figure?

Problem 3: access control pokeygram, a cutting-edge new email start-up, is setting up building access for its employees. there are two types of employees: managers and engineers, and there are three departments: security, networking, and human resoures. each employee works in a single department, and each department is housed on a different floor. managers are allowed access to any floor, while engineers are allowed access only to their own floor. there are three badge-operated elevators, each going up to only one distinct floor. every employee has one badge. pokeygram wants to use the best possible access control method in order to minimize delay for the elevators (a) access control matrix, 1. which of the following would you recommend that pokeygram use: (b) access control lists, or (c) capabilities? make sure to justify your answer. 2. what, if any, would be the benefits (and/or disadvantages) of using rbac (role-based access control) in this situation? keep your solution for this problem limited to 10-12 lines of text.

On june 3, teal company sold to chester company merchandise having a sale price of $2,600 with terms of 2/10, n/60, f.o.b. shipping point. an invoice totaling $91, terms n/30, was received by chester on june 8 from john booth transport service for the freight cost. on june 12, the company received a check for the balance due from chester company. prepare journal entries on the teal company books to record all the events noted above under each of the following bases. (1) sales and receivables are entered at gross selling price. (2) sales and receivables are entered at net of cash discounts.