How is public administration different from private management? What are the implications of these differences for the public administrator in the areas of decision-making, human resource management, and accountability?

Public administration is different from private management in that the latter focuses on maximizing shareholder wealth while the former is concerned with the general satisfaction of the public.
A public administrator has a duty to the people. He or she has to do what will make the majority happy. Most public institutions are funded by tax-payer money; therefore, there has to be transparency when it comes to decision making. The public administrator should explain to the public why they made a certain decision.
A public administrator should exhibit the highest moral standards and use the right channels when employing people. The administrator should also treat employees as resources and motivate them to serve the public.
A public administrator is usually responsible for community projects. They are accountable to the public if there's a misappropriation of public funds and resources. In addition, the public may demand the resignation of the administrator if they are found guilty of misappropriation by a court or investigative committee.

When answering this question, you will want to address each of the three areas: decision-making, human resource management, and accountability. Decision-making in any business is governed by the stakeholders of the company. The public sector serves the general population and makes decisions based on goals set by politicians and public policy. When you hear the term “red tape,” it refers to the decision making process in the public sector. There may be many hurdles to jump and stakeholders to include in a public administrator’s decisions. Private management is typically only concerned about making profits and has more leniency in making decisions within the company.
Accountability is directly related to decision-making. Public administrators have to answer to government organizations and ultimately the taxpayers. Private managers may have a board of directors or investors to question their decisions. When considering human resource management, public administration typically has more stringent guidelines for hiring and firing. Private companies, especially those with a small number of employees, may not be required to meet special guidelines or employment laws required of government positions.

Public administrators are responsible for the public good. They work in positions such as city or county manager, public works directors or commissioners, and various other offices within some kind of government bureaucracy. However, while they obviously have to be concerned with the financial well-being of whatever level of government they work in, they are not concerned with making a profit. Private management, on the other hand, is concerned with making a profit. A private manager works for a business and is usually held responsible by the business owners. Usually, in the case of a big business or corporation, these are the shareholders. There are very different factors that shape decision-making in each field. Human resource decisions might be similar when comparing smaller government structures to private management, but at the federal level, many public administrators have to work with appointees that are highly political in nature. This is not necessarily a concern of private managers, whose personnel decisions are made according to company policies designed to promote profit-making. Also, the size and scope of government projects tends to be much bigger and much longer. Public administrators often do not have as much money to offer in the way of compensation, complicating matters further. In terms of accountability, government employees may be subject to political accountability in addition to the kinds of performance reviews that are conducted in the private sector. 
https://www.powermag.com/25-differences-between-private-sector-and-government-managers/